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	$111.36	13.768%	$126.692	$126.69	$126.70	$126.70
Purchase #2	$55.59	11.844%	$62.1741	$62.17	$62.15	$62.20
Purchase #3	$215.54	8.761%	$234.4235	$234.42	$234.40	$234.40
Purchase #4	$82.75	6.554%	$88.1734	$88.17	$88.15	$88.20
Purchase #5	$20.87	4.636%	$21.8375	$21.84	$21.85	$21.80
Purchase #6	$48.51	13.192%	$54.9094	$54.91	$54.90	$54.90
Purchase #7	$99.95	12.297%	$112.2409	$112.24	$112.25	$112.20
7 purchase totals =	$634.57		$700.4508	$700.44	$700.40	$700.40