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	$99.57	11.716%	$111.2356	$111.24	$111.25	$111.20
Purchase #2	$127.71	3.427%	$132.0866	$132.09	$132.10	$132.10
Purchase #3	$60.38	11.558%	$67.3587	$67.36	$67.35	$67.40
Purchase #4	$192.52	13.516%	$218.541	$218.54	$218.55	$218.50
Purchase #5	$118.28	13.155%	$133.8397	$133.84	$133.85	$133.80
Purchase #6	$198.44	12.352%	$222.9513	$222.95	$222.95	$223.00
Purchase #7	$62.53	8.474%	$67.8288	$67.83	$67.85	$67.80
7 purchase totals =	$859.43		$953.8417	$953.85	$953.90	$953.80