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	$74.26	3.776%	$77.0641	$77.06	$77.05	$77.10
Purchase #2	$180.93	10.747%	$200.3745	$200.37	$200.35	$200.40
Purchase #3	$32.27	5.144%	$33.93	$33.93	$33.95	$33.90
Purchase #4	$29.46	3.408%	$30.464	$30.46	$30.45	$30.50
Purchase #5	$155.30	7.840%	$167.4755	$167.48	$167.50	$167.50
Purchase #6	$74.65	10.206%	$82.2688	$82.27	$82.25	$82.30
Purchase #7	$106.64	13.203%	$120.7197	$120.72	$120.70	$120.70
7 purchase totals =	$653.51		$712.2966	$712.29	$712.25	$712.40