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	$29.71	7.726%	$32.0054	$32.01	$32.00	$32.00
Purchase #2	$178.38	10.122%	$196.4356	$196.44	$196.45	$196.40
Purchase #3	$74.81	10.319%	$82.5296	$82.53	$82.55	$82.50
Purchase #4	$143.55	10.469%	$158.5782	$158.58	$158.60	$158.60
Purchase #5	$196.71	13.342%	$222.955	$222.96	$222.95	$223.00
Purchase #6	$202.49	8.374%	$219.4465	$219.45	$219.45	$219.40
Purchase #7	$84.74	4.504%	$88.5567	$88.56	$88.55	$88.60
7 purchase totals =	$910.39		$1,000.5070	$1,000.53	$1,000.55	$1,000.50