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	$200.96	8.286%	$217.6115	$217.61	$217.60	$217.60
Purchase #2	$221.76	10.256%	$244.5037	$244.50	$244.50	$244.50
Purchase #3	$9.59	12.488%	$10.7876	$10.79	$10.80	$10.80
Purchase #4	$127.87	11.354%	$142.3884	$142.39	$142.40	$142.40
Purchase #5	$30.26	9.681%	$33.1895	$33.19	$33.20	$33.20
Purchase #6	$102.63	9.352%	$112.228	$112.23	$112.25	$112.20
Purchase #7	$45.31	10.379%	$50.0127	$50.01	$50.00	$50.00
7 purchase totals =	$738.38		$810.7214	$810.72	$810.75	$810.70