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	$219.47	11.591%	$244.9088	$244.91	$244.90	$244.90
Purchase #2	$89.97	13.121%	$101.775	$101.78	$101.80	$101.80
Purchase #3	$132.80	10.179%	$146.3177	$146.32	$146.30	$146.30
Purchase #4	$154.90	11.262%	$172.3448	$172.34	$172.35	$172.30
Purchase #5	$195.38	6.706%	$208.4822	$208.48	$208.50	$208.50
Purchase #6	$36.51	3.486%	$37.7827	$37.78	$37.80	$37.80
Purchase #7	$181.40	3.857%	$188.3966	$188.40	$188.40	$188.40
7 purchase totals =	$1,010.43		$1,100.0078	$1,100.01	$1,100.05	$1,100.00