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	$75.78	8.597%	$82.2948	$82.29	$82.30	$82.30
Purchase #2	$244.95	4.788%	$256.6782	$256.68	$256.70	$256.70
Purchase #3	$76.92	13.687%	$87.448	$87.45	$87.45	$87.40
Purchase #4	$222.71	10.174%	$245.3685	$245.37	$245.35	$245.40
Purchase #5	$79.40	7.243%	$85.1509	$85.15	$85.15	$85.20
Purchase #6	$71.78	3.364%	$74.1947	$74.19	$74.20	$74.20
Purchase #7	$237.60	13.355%	$269.3315	$269.33	$269.35	$269.30
7 purchase totals =	$1,009.14		$1,100.4666	$1,100.46	$1,100.50	$1,100.50