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	$101.70	3.486%	$105.2453	$105.25	$105.25	$105.20
Purchase #2	$26.88	3.656%	$27.8627	$27.86	$27.85	$27.90
Purchase #3	$33.59	6.300%	$35.7062	$35.71	$35.70	$35.70
Purchase #4	$63.67	12.685%	$71.7465	$71.75	$71.75	$71.70
Purchase #5	$168.40	7.549%	$181.1125	$181.11	$181.10	$181.10
Purchase #6	$48.61	10.537%	$53.732	$53.73	$53.75	$53.70
Purchase #7	$133.87	4.604%	$140.0334	$140.03	$140.05	$140.00
7 purchase totals =	$576.72		$615.4386	$615.44	$615.45	$615.30