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	$134.51	8.594%	$146.0698	$146.07	$146.05	$146.10
Purchase #2	$80.45	12.684%	$90.6543	$90.65	$90.65	$90.70
Purchase #3	$75.38	3.273%	$77.8472	$77.85	$77.85	$77.80
Purchase #4	$219.36	11.873%	$245.4046	$245.40	$245.40	$245.40
Purchase #5	$19.90	4.298%	$20.7553	$20.76	$20.75	$20.80
Purchase #6	$246.60	12.275%	$276.8702	$276.87	$276.85	$276.90
Purchase #7	$218.41	11.530%	$243.5927	$243.59	$243.60	$243.60
7 purchase totals =	$994.61		$1,101.1941	$1,101.19	$1,101.15	$1,101.30