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	$147.54	6.477%	$157.0962	$157.10	$157.10	$157.10
Purchase #2	$171.91	8.854%	$187.1309	$187.13	$187.15	$187.10
Purchase #3	$18.46	12.391%	$20.7474	$20.75	$20.75	$20.70
Purchase #4	$190.93	13.516%	$216.7361	$216.74	$216.75	$216.70
Purchase #5	$37.38	3.343%	$38.6296	$38.63	$38.65	$38.60
Purchase #6	$18.54	11.402%	$20.6539	$20.65	$20.65	$20.70
Purchase #7	$56.88	4.766%	$59.5909	$59.59	$59.60	$59.60
7 purchase totals =	$641.64		$700.5850	$700.59	$700.65	$700.50