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	$119.44	10.618%	$132.1221	$132.12	$132.10	$132.10
Purchase #2	$60.81	7.642%	$65.4571	$65.46	$65.45	$65.50
Purchase #3	$55.57	6.562%	$59.2165	$59.22	$59.20	$59.20
Purchase #4	$184.92	8.550%	$200.7307	$200.73	$200.75	$200.70
Purchase #5	$162.61	4.637%	$170.1502	$170.15	$170.15	$170.20
Purchase #6	$160.42	3.680%	$166.3235	$166.32	$166.30	$166.30
Purchase #7	$69.93	5.112%	$73.5048	$73.50	$73.50	$73.50
7 purchase totals =	$813.70		$867.5049	$867.50	$867.45	$867.50