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	$249.31	4.865%	$261.4389	$261.44	$261.45	$261.40
Purchase #2	$32.79	8.588%	$35.606	$35.61	$35.60	$35.60
Purchase #3	$118.62	13.357%	$134.4641	$134.46	$134.45	$134.50
Purchase #4	$31.82	10.642%	$35.2063	$35.21	$35.20	$35.20
Purchase #5	$206.98	6.847%	$221.1519	$221.15	$221.15	$221.20
Purchase #6	$64.58	4.814%	$67.6889	$67.69	$67.70	$67.70
Purchase #7	$118.64	7.560%	$127.6092	$127.61	$127.60	$127.60
7 purchase totals =	$822.74		$883.1653	$883.17	$883.15	$883.20