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	$150.89	4.758%	$158.0693	$158.07	$158.05	$158.10
Purchase #2	$110.66	7.538%	$119.0016	$119.00	$119.00	$119.00
Purchase #3	$89.35	11.823%	$99.9139	$99.91	$99.90	$99.90
Purchase #4	$95.70	3.524%	$99.0725	$99.07	$99.05	$99.10
Purchase #5	$230.70	5.664%	$243.7668	$243.77	$243.75	$243.80
Purchase #6	$209.64	13.867%	$238.7108	$238.71	$238.70	$238.70
Purchase #7	$12.39	4.486%	$12.9458	$12.95	$12.95	$12.90
7 purchase totals =	$899.33		$971.4807	$971.48	$971.40	$971.50