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	$123.94	5.613%	$130.8968	$130.90	$130.90	$130.90
Purchase #2	$100.65	10.822%	$111.5423	$111.54	$111.55	$111.50
Purchase #3	$75.93	13.458%	$86.1487	$86.15	$86.15	$86.10
Purchase #4	$55.64	3.404%	$57.534	$57.53	$57.55	$57.50
Purchase #5	$185.91	12.697%	$209.515	$209.52	$209.50	$209.50
Purchase #6	$95.94	10.609%	$106.1183	$106.12	$106.10	$106.10
Purchase #7	$57.38	5.692%	$60.6461	$60.65	$60.65	$60.60
7 purchase totals =	$695.39		$762.4012	$762.41	$762.40	$762.20