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	$50.43	9.748%	$55.3459	$55.35	$55.35	$55.30
Purchase #2	$131.79	13.729%	$149.8834	$149.88	$149.90	$149.90
Purchase #3	$140.30	4.597%	$146.7496	$146.75	$146.75	$146.70
Purchase #4	$187.38	11.370%	$208.6851	$208.69	$208.70	$208.70
Purchase #5	$207.56	8.701%	$225.6198	$225.62	$225.60	$225.60
Purchase #6	$188.43	4.257%	$196.4515	$196.45	$196.45	$196.50
Purchase #7	$85.69	5.511%	$90.4124	$90.41	$90.40	$90.40
7 purchase totals =	$991.58		$1,073.1477	$1,073.15	$1,073.15	$1,073.10