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	$200.43	4.629%	$209.7079	$209.71	$209.70	$209.70
Purchase #2	$78.92	9.144%	$86.1364	$86.14	$86.15	$86.10
Purchase #3	$155.99	12.521%	$175.5215	$175.52	$175.50	$175.50
Purchase #4	$17.89	9.231%	$19.5414	$19.54	$19.55	$19.50
Purchase #5	$211.87	7.734%	$228.256	$228.26	$228.25	$228.30
Purchase #6	$20.55	4.522%	$21.4793	$21.48	$21.50	$21.50
Purchase #7	$217.28	5.503%	$229.2369	$229.24	$229.25	$229.20
7 purchase totals =	$902.93		$969.8794	$969.89	$969.90	$969.80