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	$127.43	11.392%	$141.9468	$141.95	$141.95	$141.90
Purchase #2	$31.98	4.814%	$33.5195	$33.52	$33.50	$33.50
Purchase #3	$118.50	11.682%	$132.3432	$132.34	$132.35	$132.30
Purchase #4	$58.30	5.165%	$61.3112	$61.31	$61.30	$61.30
Purchase #5	$85.67	10.247%	$94.4486	$94.45	$94.45	$94.40
Purchase #6	$162.95	5.152%	$171.3452	$171.35	$171.35	$171.30
Purchase #7	$150.79	10.451%	$166.5491	$166.55	$166.55	$166.50
7 purchase totals =	$735.62		$801.4636	$801.47	$801.45	$801.20