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	$131.91	12.812%	$148.8103	$148.81	$148.80	$148.80
Purchase #2	$243.42	6.277%	$258.6995	$258.70	$258.70	$258.70
Purchase #3	$78.70	6.114%	$83.5117	$83.51	$83.50	$83.50
Purchase #4	$17.52	10.656%	$19.3869	$19.39	$19.40	$19.40
Purchase #5	$37.83	13.677%	$43.004	$43.00	$43.00	$43.00
Purchase #6	$236.62	11.742%	$264.4039	$264.40	$264.40	$264.40
Purchase #7	$195.72	10.506%	$216.2823	$216.28	$216.30	$216.30
7 purchase totals =	$941.72		$1,034.0986	$1,034.09	$1,034.10	$1,034.10