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	$208.27	8.120%	$225.1815	$225.18	$225.20	$225.20
Purchase #2	$227.35	13.653%	$258.3901	$258.39	$258.40	$258.40
Purchase #3	$183.27	8.661%	$199.143	$199.14	$199.15	$199.10
Purchase #4	$244.32	7.408%	$262.4192	$262.42	$262.40	$262.40
Purchase #5	$85.85	3.846%	$89.1518	$89.15	$89.15	$89.20
Purchase #6	$182.64	8.324%	$197.843	$197.84	$197.85	$197.80
Purchase #7	$47.33	6.601%	$50.4543	$50.45	$50.45	$50.50
7 purchase totals =	$1,179.03		$1,282.5829	$1,282.57	$1,282.60	$1,282.60