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	$66.39	11.351%	$73.9259	$73.93	$73.95	$73.90
Purchase #2	$107.50	7.369%	$115.4217	$115.42	$115.40	$115.40
Purchase #3	$79.66	11.301%	$88.6624	$88.66	$88.65	$88.70
Purchase #4	$244.34	5.874%	$258.6925	$258.69	$258.70	$258.70
Purchase #5	$243.78	5.357%	$256.8393	$256.84	$256.85	$256.80
Purchase #6	$236.77	11.593%	$264.2187	$264.22	$264.20	$264.20
Purchase #7	$39.27	8.435%	$42.5824	$42.58	$42.60	$42.60
7 purchase totals =	$1,017.71		$1,100.3429	$1,100.34	$1,100.35	$1,100.30