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	$100.65	10.229%	$110.9455	$110.95	$110.95	$110.90
Purchase #2	$50.83	11.664%	$56.7588	$56.76	$56.75	$56.80
Purchase #3	$101.56	10.339%	$112.0603	$112.06	$112.05	$112.10
Purchase #4	$198.48	10.131%	$218.588	$218.59	$218.60	$218.60
Purchase #5	$195.96	6.304%	$208.3133	$208.31	$208.30	$208.30
Purchase #6	$142.52	7.682%	$153.4684	$153.47	$153.45	$153.50
Purchase #7	$58.94	4.507%	$61.5964	$61.60	$61.60	$61.60
7 purchase totals =	$848.94		$921.7307	$921.74	$921.70	$921.80