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	$85.38	4.733%	$89.421	$89.42	$89.40	$89.40
Purchase #2	$162.48	13.429%	$184.2994	$184.30	$184.30	$184.30
Purchase #3	$9.43	8.648%	$10.2455	$10.25	$10.25	$10.20
Purchase #4	$67.40	7.336%	$72.3445	$72.34	$72.35	$72.30
Purchase #5	$11.64	4.633%	$12.1793	$12.18	$12.20	$12.20
Purchase #6	$93.80	10.126%	$103.2982	$103.30	$103.30	$103.30
Purchase #7	$131.68	11.294%	$146.5519	$146.55	$146.55	$146.60
7 purchase totals =	$561.81		$618.3398	$618.34	$618.35	$618.30