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	$30.80	7.192%	$33.0151	$33.02	$33.00	$33.00
Purchase #2	$96.27	4.202%	$100.3153	$100.32	$100.30	$100.30
Purchase #3	$147.38	4.671%	$154.2641	$154.26	$154.25	$154.30
Purchase #4	$32.91	13.467%	$37.342	$37.34	$37.35	$37.30
Purchase #5	$212.44	13.564%	$241.2554	$241.26	$241.25	$241.30
Purchase #6	$222.44	12.634%	$250.5431	$250.54	$250.55	$250.50
Purchase #7	$126.72	3.532%	$131.1958	$131.20	$131.20	$131.20
7 purchase totals =	$868.96		$947.9308	$947.94	$947.90	$947.90