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	$166.52	10.699%	$184.336	$184.34	$184.35	$184.30
Purchase #2	$153.58	7.783%	$165.5331	$165.53	$165.55	$165.50
Purchase #3	$85.31	6.540%	$90.8893	$90.89	$90.90	$90.90
Purchase #4	$31.47	10.459%	$34.7614	$34.76	$34.75	$34.80
Purchase #5	$70.52	8.406%	$76.4479	$76.45	$76.45	$76.40
Purchase #6	$140.70	13.398%	$159.551	$159.55	$159.55	$159.60
Purchase #7	$199.31	7.769%	$214.7944	$214.79	$214.80	$214.80
7 purchase totals =	$847.41		$926.3131	$926.31	$926.35	$926.30