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	$79.90	12.207%	$89.6534	$89.65	$89.65	$89.70
Purchase #2	$64.89	12.279%	$72.8578	$72.86	$72.85	$72.90
Purchase #3	$160.48	3.759%	$166.5124	$166.51	$166.50	$166.50
Purchase #4	$164.66	4.625%	$172.2755	$172.28	$172.30	$172.30
Purchase #5	$237.28	10.617%	$262.472	$262.47	$262.45	$262.50
Purchase #6	$250.28	10.805%	$277.3228	$277.32	$277.30	$277.30
Purchase #7	$47.48	10.433%	$52.4336	$52.43	$52.45	$52.40
7 purchase totals =	$1,004.97		$1,093.5275	$1,093.52	$1,093.50	$1,093.60