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	$128.28	3.642%	$132.952	$132.95	$132.95	$133.00
Purchase #2	$235.46	12.338%	$264.5111	$264.51	$264.50	$264.50
Purchase #3	$156.57	5.779%	$165.6182	$165.62	$165.60	$165.60
Purchase #4	$180.81	13.322%	$204.8975	$204.90	$204.90	$204.90
Purchase #5	$101.78	4.491%	$106.3509	$106.35	$106.35	$106.40
Purchase #6	$75.48	13.851%	$85.9347	$85.93	$85.95	$85.90
Purchase #7	$89.75	12.651%	$101.1043	$101.10	$101.10	$101.10
7 purchase totals =	$968.13		$1,061.3687	$1,061.36	$1,061.35	$1,061.40