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	$80.79	9.681%	$88.6113	$88.61	$88.60	$88.60
Purchase #2	$245.82	7.261%	$263.669	$263.67	$263.65	$263.70
Purchase #3	$23.75	13.330%	$26.9159	$26.92	$26.90	$26.90
Purchase #4	$118.80	7.165%	$127.312	$127.31	$127.30	$127.30
Purchase #5	$31.88	9.518%	$34.9143	$34.91	$34.90	$34.90
Purchase #6	$106.81	4.510%	$111.6271	$111.63	$111.65	$111.60
Purchase #7	$93.26	13.118%	$105.4938	$105.49	$105.50	$105.50
7 purchase totals =	$701.11		$758.5434	$758.54	$758.50	$758.50