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	$235.59	3.629%	$244.1396	$244.14	$244.15	$244.10
Purchase #2	$68.89	7.801%	$74.2641	$74.26	$74.25	$74.30
Purchase #3	$13.91	12.413%	$15.6366	$15.64	$15.65	$15.60
Purchase #4	$61.39	13.715%	$69.8096	$69.81	$69.80	$69.80
Purchase #5	$173.86	13.215%	$196.8356	$196.84	$196.85	$196.80
Purchase #6	$31.43	3.416%	$32.5036	$32.50	$32.50	$32.50
Purchase #7	$39.53	6.430%	$42.0718	$42.07	$42.05	$42.10
7 purchase totals =	$624.60		$675.2609	$675.26	$675.25	$675.20