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	$179.58	11.824%	$200.8135	$200.81	$200.80	$200.80
Purchase #2	$32.71	7.526%	$35.1718	$35.17	$35.15	$35.20
Purchase #3	$201.85	12.698%	$227.4809	$227.48	$227.50	$227.50
Purchase #4	$170.63	7.121%	$182.7806	$182.78	$182.80	$182.80
Purchase #5	$93.94	10.217%	$103.5378	$103.54	$103.55	$103.50
Purchase #6	$184.92	5.377%	$194.8631	$194.86	$194.85	$194.90
Purchase #7	$128.55	3.855%	$133.5056	$133.51	$133.50	$133.50
7 purchase totals =	$992.18		$1,078.1533	$1,078.15	$1,078.15	$1,078.20