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	$100.85	7.270%	$108.1818	$108.18	$108.20	$108.20
Purchase #2	$11.56	9.300%	$12.6351	$12.64	$12.65	$12.60
Purchase #3	$31.93	4.679%	$33.424	$33.42	$33.40	$33.40
Purchase #4	$46.30	13.337%	$52.475	$52.48	$52.50	$52.50
Purchase #5	$188.45	12.288%	$211.6067	$211.61	$211.60	$211.60
Purchase #6	$132.47	13.802%	$150.7535	$150.75	$150.75	$150.80
Purchase #7	$105.52	4.619%	$110.394	$110.39	$110.40	$110.40
7 purchase totals =	$617.08		$679.4701	$679.47	$679.50	$679.50