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	$115.82	3.244%	$119.5772	$119.58	$119.60	$119.60
Purchase #2	$188.46	10.691%	$208.6083	$208.61	$208.60	$208.60
Purchase #3	$124.73	13.810%	$141.9552	$141.96	$141.95	$142.00
Purchase #4	$19.74	4.511%	$20.6305	$20.63	$20.65	$20.60
Purchase #5	$221.60	5.143%	$232.9969	$233.00	$233.00	$233.00
Purchase #6	$172.75	10.750%	$191.3206	$191.32	$191.30	$191.30
Purchase #7	$133.87	13.333%	$151.7189	$151.72	$151.70	$151.70
7 purchase totals =	$976.97		$1,066.8076	$1,066.82	$1,066.80	$1,066.80