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	$180.62	11.628%	$201.6225	$201.62	$201.60	$201.60
Purchase #2	$236.54	3.766%	$245.4481	$245.45	$245.45	$245.40
Purchase #3	$146.29	9.319%	$159.9228	$159.92	$159.90	$159.90
Purchase #4	$136.72	13.738%	$155.5026	$155.50	$155.50	$155.50
Purchase #5	$133.90	12.437%	$150.5531	$150.55	$150.55	$150.60
Purchase #6	$140.82	11.339%	$156.7876	$156.79	$156.80	$156.80
Purchase #7	$173.56	6.455%	$184.7633	$184.76	$184.75	$184.80
7 purchase totals =	$1,148.45		$1,254.6000	$1,254.59	$1,254.55	$1,254.60