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	$144.67	12.828%	$163.2283	$163.23	$163.25	$163.20
Purchase #2	$92.75	7.316%	$99.5356	$99.54	$99.55	$99.50
Purchase #3	$32.55	13.734%	$37.0204	$37.02	$37.00	$37.00
Purchase #4	$109.35	13.257%	$123.8465	$123.85	$123.85	$123.80
Purchase #5	$119.59	11.438%	$133.2687	$133.27	$133.25	$133.30
Purchase #6	$49.82	13.740%	$56.6653	$56.67	$56.65	$56.70
Purchase #7	$139.46	12.820%	$157.3388	$157.34	$157.35	$157.30
7 purchase totals =	$688.19		$770.9036	$770.92	$770.90	$770.80