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	$229.31	13.430%	$260.1063	$260.11	$260.10	$260.10
Purchase #2	$105.35	7.778%	$113.5441	$113.54	$113.55	$113.50
Purchase #3	$199.66	11.375%	$222.3713	$222.37	$222.35	$222.40
Purchase #4	$190.93	7.557%	$205.3586	$205.36	$205.35	$205.40
Purchase #5	$56.74	9.123%	$61.9164	$61.92	$61.90	$61.90
Purchase #6	$85.54	5.743%	$90.4526	$90.45	$90.45	$90.50
Purchase #7	$88.35	12.850%	$99.703	$99.70	$99.70	$99.70
7 purchase totals =	$955.88		$1,053.4523	$1,053.45	$1,053.40	$1,053.50