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	$156.60	5.647%	$165.4432	$165.44	$165.45	$165.40
Purchase #2	$87.90	12.777%	$99.131	$99.13	$99.15	$99.10
Purchase #3	$209.56	4.336%	$218.6465	$218.65	$218.65	$218.60
Purchase #4	$165.77	10.703%	$183.5124	$183.51	$183.50	$183.50
Purchase #5	$214.57	11.231%	$238.6684	$238.67	$238.65	$238.70
Purchase #6	$35.25	11.273%	$39.2237	$39.22	$39.20	$39.20
Purchase #7	$231.86	5.116%	$243.722	$243.72	$243.70	$243.70
7 purchase totals =	$1,101.51		$1,188.3472	$1,188.34	$1,188.30	$1,188.20