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	$235.94	11.310%	$262.6248	$262.62	$262.60	$262.60
Purchase #2	$62.40	9.733%	$68.4734	$68.47	$68.45	$68.50
Purchase #3	$162.72	4.195%	$169.5461	$169.55	$169.55	$169.50
Purchase #4	$212.38	13.257%	$240.5352	$240.54	$240.55	$240.50
Purchase #5	$31.29	7.732%	$33.7093	$33.71	$33.70	$33.70
Purchase #6	$236.33	12.157%	$265.0606	$265.06	$265.05	$265.10
Purchase #7	$55.42	10.147%	$61.0435	$61.04	$61.05	$61.00
7 purchase totals =	$996.48		$1,100.9929	$1,100.99	$1,100.95	$1,100.90