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	$172.57	7.501%	$185.5145	$185.51	$185.50	$185.50
Purchase #2	$144.59	5.150%	$152.0364	$152.04	$152.05	$152.00
Purchase #3	$10.99	7.496%	$11.8138	$11.81	$11.80	$11.80
Purchase #4	$15.56	6.155%	$16.5177	$16.52	$16.50	$16.50
Purchase #5	$190.41	5.190%	$200.2923	$200.29	$200.30	$200.30
Purchase #6	$146.54	10.531%	$161.9721	$161.97	$161.95	$162.00
Purchase #7	$130.69	6.449%	$139.1182	$139.12	$139.10	$139.10
7 purchase totals =	$811.35		$867.2650	$867.26	$867.20	$867.20