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	$53.25	11.672%	$59.4653	$59.47	$59.45	$59.50
Purchase #2	$77.50	12.200%	$86.955	$86.96	$86.95	$87.00
Purchase #3	$73.37	6.479%	$78.1236	$78.12	$78.10	$78.10
Purchase #4	$190.98	12.854%	$215.5286	$215.53	$215.55	$215.50
Purchase #5	$199.78	4.515%	$208.8001	$208.80	$208.80	$208.80
Purchase #6	$82.44	13.345%	$93.4416	$93.44	$93.45	$93.40
Purchase #7	$74.68	3.287%	$77.1347	$77.13	$77.15	$77.10
7 purchase totals =	$752.00		$819.4489	$819.45	$819.45	$819.40