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	$76.91	7.819%	$82.9236	$82.92	$82.90	$82.90
Purchase #2	$139.87	8.420%	$151.6471	$151.65	$151.65	$151.60
Purchase #3	$26.47	7.762%	$28.5246	$28.52	$28.50	$28.50
Purchase #4	$232.50	13.534%	$263.9666	$263.97	$263.95	$264.00
Purchase #5	$50.33	7.251%	$53.9794	$53.98	$54.00	$54.00
Purchase #6	$138.39	9.841%	$152.009	$152.01	$152.00	$152.00
Purchase #7	$163.68	11.146%	$181.9238	$181.92	$181.90	$181.90
7 purchase totals =	$828.15		$914.9741	$914.97	$914.90	$914.90