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	$81.94	11.852%	$91.6515	$91.65	$91.65	$91.70
Purchase #2	$53.72	5.766%	$56.8175	$56.82	$56.80	$56.80
Purchase #3	$63.63	6.759%	$67.9308	$67.93	$67.95	$67.90
Purchase #4	$42.74	13.627%	$48.5642	$48.56	$48.55	$48.60
Purchase #5	$215.73	5.836%	$228.32	$228.32	$228.30	$228.30
Purchase #6	$146.26	4.563%	$152.9338	$152.93	$152.95	$152.90
Purchase #7	$38.76	5.155%	$40.7581	$40.76	$40.75	$40.80
7 purchase totals =	$642.78		$686.9759	$686.97	$686.95	$687.00