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	$83.78	6.219%	$88.9903	$88.99	$89.00	$89.00
Purchase #2	$33.57	11.596%	$37.4628	$37.46	$37.45	$37.50
Purchase #3	$77.85	12.701%	$87.7377	$87.74	$87.75	$87.70
Purchase #4	$176.81	13.761%	$201.1408	$201.14	$201.15	$201.10
Purchase #5	$63.51	10.285%	$70.042	$70.04	$70.05	$70.00
Purchase #6	$174.29	8.377%	$188.8903	$188.89	$188.90	$188.90
Purchase #7	$54.63	8.594%	$59.3249	$59.32	$59.30	$59.30
7 purchase totals =	$664.44		$733.5888	$733.58	$733.60	$733.50