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	$125.54	5.753%	$132.7623	$132.76	$132.75	$132.80
Purchase #2	$201.93	8.597%	$219.2899	$219.29	$219.30	$219.30
Purchase #3	$96.49	4.121%	$100.4664	$100.47	$100.45	$100.50
Purchase #4	$148.35	4.428%	$154.9189	$154.92	$154.90	$154.90
Purchase #5	$152.46	6.870%	$162.934	$162.93	$162.95	$162.90
Purchase #6	$48.92	11.457%	$54.5248	$54.52	$54.50	$54.50
Purchase #7	$65.80	11.626%	$73.4499	$73.45	$73.45	$73.40
7 purchase totals =	$839.49		$898.3462	$898.34	$898.30	$898.30