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	$73.56	11.579%	$82.0775	$82.08	$82.10	$82.10
Purchase #2	$165.51	8.626%	$179.7869	$179.79	$179.80	$179.80
Purchase #3	$247.70	10.502%	$273.7135	$273.71	$273.70	$273.70
Purchase #4	$101.69	6.571%	$108.372	$108.37	$108.35	$108.40
Purchase #5	$14.39	10.102%	$15.8437	$15.84	$15.85	$15.80
Purchase #6	$242.98	5.742%	$256.9319	$256.93	$256.95	$256.90
Purchase #7	$148.67	11.243%	$165.385	$165.39	$165.40	$165.40
7 purchase totals =	$994.50		$1,082.1105	$1,082.11	$1,082.15	$1,082.10