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	$81.63	4.540%	$85.336	$85.34	$85.35	$85.30
Purchase #2	$235.31	9.686%	$258.1021	$258.10	$258.10	$258.10
Purchase #3	$15.55	3.759%	$16.1345	$16.13	$16.15	$16.10
Purchase #4	$83.30	6.134%	$88.4096	$88.41	$88.40	$88.40
Purchase #5	$127.31	11.118%	$141.4643	$141.46	$141.45	$141.50
Purchase #6	$239.40	4.612%	$250.4411	$250.44	$250.45	$250.40
Purchase #7	$231.98	5.588%	$244.943	$244.94	$244.95	$244.90
7 purchase totals =	$1,014.48		$1,084.8306	$1,084.82	$1,084.85	$1,084.70