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	$105.56	6.643%	$112.5724	$112.57	$112.55	$112.60
Purchase #2	$212.47	8.412%	$230.343	$230.34	$230.35	$230.30
Purchase #3	$9.26	13.380%	$10.499	$10.50	$10.50	$10.50
Purchase #4	$89.69	3.177%	$92.5395	$92.54	$92.55	$92.50
Purchase #5	$45.41	4.609%	$47.5029	$47.50	$47.50	$47.50
Purchase #6	$151.69	8.155%	$164.0603	$164.06	$164.05	$164.10
Purchase #7	$53.50	7.139%	$57.3194	$57.32	$57.30	$57.30
7 purchase totals =	$667.58		$714.8365	$714.83	$714.80	$714.80