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	$162.87	3.583%	$168.7056	$168.71	$168.70	$168.70
Purchase #2	$131.41	5.357%	$138.4496	$138.45	$138.45	$138.40
Purchase #3	$186.30	13.179%	$210.8525	$210.85	$210.85	$210.90
Purchase #4	$115.40	4.675%	$120.795	$120.80	$120.80	$120.80
Purchase #5	$153.31	12.639%	$172.6869	$172.69	$172.70	$172.70
Purchase #6	$64.95	8.138%	$70.2356	$70.24	$70.25	$70.20
Purchase #7	$70.59	3.125%	$72.7959	$72.80	$72.80	$72.80
7 purchase totals =	$884.83		$954.5211	$954.54	$954.55	$954.50