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	$205.32	4.195%	$213.9332	$213.93	$213.95	$213.90
Purchase #2	$171.29	8.132%	$185.2193	$185.22	$185.20	$185.20
Purchase #3	$79.69	13.165%	$90.1812	$90.18	$90.20	$90.20
Purchase #4	$42.78	9.293%	$46.7555	$46.76	$46.75	$46.80
Purchase #5	$83.67	10.525%	$92.4763	$92.48	$92.50	$92.50
Purchase #6	$184.76	3.768%	$191.7218	$191.72	$191.70	$191.70
Purchase #7	$135.55	13.593%	$153.9753	$153.98	$154.00	$154.00
7 purchase totals =	$903.06		$974.2626	$974.27	$974.30	$974.30