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	$97.27	13.490%	$110.3917	$110.39	$110.40	$110.40
Purchase #2	$200.59	10.447%	$221.5456	$221.55	$221.55	$221.50
Purchase #3	$70.57	3.871%	$73.3018	$73.30	$73.30	$73.30
Purchase #4	$139.89	7.595%	$150.5146	$150.51	$150.50	$150.50
Purchase #5	$245.92	12.730%	$277.2256	$277.23	$277.25	$277.20
Purchase #6	$153.38	11.751%	$171.4037	$171.40	$171.40	$171.40
Purchase #7	$192.70	3.858%	$200.1344	$200.13	$200.15	$200.10
7 purchase totals =	$1,100.32		$1,204.5174	$1,204.51	$1,204.55	$1,204.40