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	$132.74	9.576%	$145.4512	$145.45	$145.45	$145.50
Purchase #2	$6.88	9.119%	$7.5074	$7.51	$7.50	$7.50
Purchase #3	$244.39	8.325%	$264.7355	$264.74	$264.75	$264.70
Purchase #4	$79.53	7.596%	$85.5711	$85.57	$85.55	$85.60
Purchase #5	$22.80	4.311%	$23.7829	$23.78	$23.80	$23.80
Purchase #6	$160.72	10.851%	$178.1597	$178.16	$178.15	$178.20
Purchase #7	$54.33	9.852%	$59.6826	$59.68	$59.70	$59.70
7 purchase totals =	$701.39		$764.8904	$764.89	$764.90	$765.00