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	$156.58	11.546%	$174.6587	$174.66	$174.65	$174.70
Purchase #2	$101.73	3.748%	$105.5428	$105.54	$105.55	$105.50
Purchase #3	$71.35	11.656%	$79.6666	$79.67	$79.65	$79.70
Purchase #4	$91.41	9.780%	$100.3499	$100.35	$100.35	$100.30
Purchase #5	$165.47	11.291%	$184.1532	$184.15	$184.15	$184.20
Purchase #6	$79.75	12.317%	$89.5728	$89.57	$89.55	$89.60
Purchase #7	$169.86	7.239%	$182.1562	$182.16	$182.15	$182.20
7 purchase totals =	$836.15		$916.1002	$916.10	$916.05	$916.20