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	$187.99	12.158%	$210.8458	$210.85	$210.85	$210.80
Purchase #2	$130.38	8.816%	$141.8743	$141.87	$141.85	$141.90
Purchase #3	$180.88	7.737%	$194.8747	$194.87	$194.85	$194.90
Purchase #4	$93.92	12.105%	$105.289	$105.29	$105.30	$105.30
Purchase #5	$162.32	6.511%	$172.8887	$172.89	$172.90	$172.90
Purchase #6	$157.97	5.559%	$166.7516	$166.75	$166.75	$166.80
Purchase #7	$48.36	10.619%	$53.4953	$53.50	$53.50	$53.50
7 purchase totals =	$961.82		$1,046.0194	$1,046.02	$1,046.00	$1,046.10