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	$52.62	13.533%	$59.7411	$59.74	$59.75	$59.70
Purchase #2	$247.36	13.810%	$281.5204	$281.52	$281.50	$281.50
Purchase #3	$153.83	9.478%	$168.41	$168.41	$168.40	$168.40
Purchase #4	$6.25	8.840%	$6.8025	$6.80	$6.80	$6.80
Purchase #5	$250.72	7.263%	$268.9298	$268.93	$268.95	$268.90
Purchase #6	$60.76	11.390%	$67.6806	$67.68	$67.70	$67.70
Purchase #7	$89.52	13.514%	$101.6177	$101.62	$101.60	$101.60
7 purchase totals =	$861.06		$954.7021	$954.70	$954.70	$954.60