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	$70.85	3.717%	$73.4835	$73.48	$73.50	$73.50
Purchase #2	$96.33	6.467%	$102.5597	$102.56	$102.55	$102.60
Purchase #3	$150.52	5.516%	$158.8227	$158.82	$158.80	$158.80
Purchase #4	$131.77	4.502%	$137.7023	$137.70	$137.70	$137.70
Purchase #5	$199.86	5.567%	$210.9862	$210.99	$211.00	$211.00
Purchase #6	$146.83	8.155%	$158.804	$158.80	$158.80	$158.80
Purchase #7	$184.56	6.275%	$196.1411	$196.14	$196.15	$196.10
7 purchase totals =	$980.72		$1,038.4995	$1,038.49	$1,038.50	$1,038.50