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	$132.71	13.347%	$150.4228	$150.42	$150.40	$150.40
Purchase #2	$175.83	3.846%	$182.5924	$182.59	$182.60	$182.60
Purchase #3	$51.89	4.283%	$54.1124	$54.11	$54.10	$54.10
Purchase #4	$86.28	10.240%	$95.1151	$95.12	$95.10	$95.10
Purchase #5	$40.84	7.290%	$43.8172	$43.82	$43.80	$43.80
Purchase #6	$121.82	6.841%	$130.1537	$130.15	$130.15	$130.20
Purchase #7	$222.34	12.498%	$250.1281	$250.13	$250.15	$250.10
7 purchase totals =	$831.71		$906.3417	$906.34	$906.30	$906.30