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	$59.30	13.717%	$67.4342	$67.43	$67.45	$67.40
Purchase #2	$204.63	11.498%	$228.1584	$228.16	$228.15	$228.20
Purchase #3	$32.68	3.549%	$33.8398	$33.84	$33.85	$33.80
Purchase #4	$99.55	11.831%	$111.3278	$111.33	$111.35	$111.30
Purchase #5	$84.48	13.798%	$96.1366	$96.14	$96.15	$96.10
Purchase #6	$154.89	12.765%	$174.6617	$174.66	$174.65	$174.70
Purchase #7	$31.51	6.670%	$33.6117	$33.61	$33.60	$33.60
7 purchase totals =	$667.04		$745.1702	$745.17	$745.20	$745.10