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	$162.59	11.403%	$181.1301	$181.13	$181.15	$181.10
Purchase #2	$203.41	6.500%	$216.6317	$216.63	$216.65	$216.60
Purchase #3	$85.39	6.289%	$90.7602	$90.76	$90.75	$90.80
Purchase #4	$52.56	12.534%	$59.1479	$59.15	$59.15	$59.10
Purchase #5	$97.35	5.779%	$102.9759	$102.98	$103.00	$103.00
Purchase #6	$52.98	8.551%	$57.5103	$57.51	$57.50	$57.50
Purchase #7	$195.66	13.335%	$221.7513	$221.75	$221.75	$221.80
7 purchase totals =	$849.94		$929.9074	$929.91	$929.95	$929.90