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	$55.74	7.488%	$59.9138	$59.91	$59.90	$59.90
Purchase #2	$26.62	10.593%	$29.4399	$29.44	$29.45	$29.40
Purchase #3	$75.37	5.661%	$79.6367	$79.64	$79.65	$79.60
Purchase #4	$31.81	11.704%	$35.533	$35.53	$35.55	$35.50
Purchase #5	$8.66	8.180%	$9.3684	$9.37	$9.35	$9.40
Purchase #6	$119.49	10.259%	$131.7485	$131.75	$131.75	$131.70
Purchase #7	$99.71	11.327%	$111.0042	$111.00	$111.00	$111.00
7 purchase totals =	$417.40		$456.6445	$456.64	$456.65	$456.50