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	$111.28	4.467%	$116.2509	$116.25	$116.25	$116.30
Purchase #2	$155.69	7.616%	$167.5474	$167.55	$167.55	$167.50
Purchase #3	$29.57	3.873%	$30.7152	$30.72	$30.70	$30.70
Purchase #4	$190.36	3.404%	$196.8399	$196.84	$196.85	$196.80
Purchase #5	$19.89	4.213%	$20.728	$20.73	$20.75	$20.70
Purchase #6	$191.69	5.450%	$202.1371	$202.14	$202.15	$202.10
Purchase #7	$98.44	13.563%	$111.7914	$111.79	$111.80	$111.80
7 purchase totals =	$796.92		$846.0099	$846.02	$846.05	$845.90