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	$144.80	10.230%	$159.613	$159.61	$159.60	$159.60
Purchase #2	$77.40	7.148%	$82.9326	$82.93	$82.95	$82.90
Purchase #3	$93.39	4.148%	$97.2638	$97.26	$97.25	$97.30
Purchase #4	$81.74	9.530%	$89.5298	$89.53	$89.55	$89.50
Purchase #5	$200.52	10.591%	$221.7571	$221.76	$221.75	$221.80
Purchase #6	$190.82	11.183%	$212.1594	$212.16	$212.15	$212.20
Purchase #7	$140.28	10.176%	$154.5549	$154.55	$154.55	$154.60
7 purchase totals =	$928.95		$1,017.8106	$1,017.80	$1,017.80	$1,017.90