Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$109.41	7.583%	$117.7066	$117.71	$117.70	$117.70
Purchase #2	$109.51	4.127%	$114.0295	$114.03	$114.05	$114.00
Purchase #3	$112.25	13.630%	$127.5497	$127.55	$127.55	$127.50
Purchase #4	$180.90	4.616%	$189.2503	$189.25	$189.25	$189.30
Purchase #5	$149.99	11.596%	$167.3828	$167.38	$167.40	$167.40
Purchase #6	$188.30	3.316%	$194.544	$194.54	$194.55	$194.50
Purchase #7	$165.98	12.416%	$186.5881	$186.59	$186.60	$186.60
7 purchase totals =	$1,016.34		$1,097.0510	$1,097.05	$1,097.10	$1,097.00