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	$127.41	13.184%	$144.2077	$144.21	$144.20	$144.20
Purchase #2	$146.94	3.474%	$152.0447	$152.04	$152.05	$152.00
Purchase #3	$13.58	13.461%	$15.408	$15.41	$15.40	$15.40
Purchase #4	$45.40	10.809%	$50.3073	$50.31	$50.30	$50.30
Purchase #5	$79.89	3.432%	$82.6318	$82.63	$82.65	$82.60
Purchase #6	$34.36	6.446%	$36.5748	$36.57	$36.55	$36.60
Purchase #7	$7.54	4.325%	$7.8661	$7.87	$7.85	$7.90
7 purchase totals =	$455.12		$489.0404	$489.04	$489.00	$489.00