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	$148.75	6.741%	$158.7772	$158.78	$158.80	$158.80
Purchase #2	$218.69	13.773%	$248.8102	$248.81	$248.80	$248.80
Purchase #3	$90.76	4.862%	$95.1728	$95.17	$95.15	$95.20
Purchase #4	$55.70	7.169%	$59.6931	$59.69	$59.70	$59.70
Purchase #5	$209.64	13.796%	$238.5619	$238.56	$238.55	$238.60
Purchase #6	$230.89	12.380%	$259.4742	$259.47	$259.45	$259.50
Purchase #7	$249.54	13.279%	$282.6764	$282.68	$282.70	$282.70
7 purchase totals =	$1,203.97		$1,343.1658	$1,343.16	$1,343.15	$1,343.30