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	$141.28	9.684%	$154.9616	$154.96	$154.95	$155.00
Purchase #2	$25.74	5.317%	$27.1086	$27.11	$27.10	$27.10
Purchase #3	$83.56	8.535%	$90.6918	$90.69	$90.70	$90.70
Purchase #4	$29.87	9.673%	$32.7593	$32.76	$32.75	$32.80
Purchase #5	$159.60	4.624%	$166.9799	$166.98	$167.00	$167.00
Purchase #6	$195.67	13.542%	$222.1676	$222.17	$222.15	$222.20
Purchase #7	$86.57	5.816%	$91.6049	$91.60	$91.60	$91.60
7 purchase totals =	$722.29		$786.2737	$786.27	$786.25	$786.40