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	$205.69	8.341%	$222.8466	$222.85	$222.85	$222.80
Purchase #2	$19.30	3.192%	$19.9161	$19.92	$19.90	$19.90
Purchase #3	$131.78	11.659%	$147.1442	$147.14	$147.15	$147.10
Purchase #4	$72.76	9.638%	$79.7726	$79.77	$79.75	$79.80
Purchase #5	$211.42	3.305%	$218.4074	$218.41	$218.40	$218.40
Purchase #6	$101.78	9.126%	$111.0684	$111.07	$111.05	$111.10
Purchase #7	$85.90	4.641%	$89.8866	$89.89	$89.90	$89.90
7 purchase totals =	$828.63		$889.0419	$889.05	$889.00	$889.00