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	$173.72	6.801%	$185.5347	$185.53	$185.55	$185.50
Purchase #2	$57.56	10.834%	$63.7961	$63.80	$63.80	$63.80
Purchase #3	$70.38	11.546%	$78.5061	$78.51	$78.50	$78.50
Purchase #4	$163.98	3.770%	$170.162	$170.16	$170.15	$170.20
Purchase #5	$26.34	7.604%	$28.3429	$28.34	$28.35	$28.30
Purchase #6	$236.92	7.610%	$254.9496	$254.95	$254.95	$254.90
Purchase #7	$112.89	3.844%	$117.2295	$117.23	$117.25	$117.20
7 purchase totals =	$841.79		$898.5209	$898.52	$898.55	$898.40