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	$66.42	8.651%	$72.166	$72.17	$72.15	$72.20
Purchase #2	$104.28	12.404%	$117.2149	$117.21	$117.20	$117.20
Purchase #3	$95.28	4.222%	$99.3027	$99.30	$99.30	$99.30
Purchase #4	$106.72	6.283%	$113.4252	$113.43	$113.45	$113.40
Purchase #5	$221.30	4.600%	$231.4798	$231.48	$231.50	$231.50
Purchase #6	$47.61	5.145%	$50.0595	$50.06	$50.05	$50.10
Purchase #7	$26.63	8.168%	$28.8051	$28.81	$28.80	$28.80
7 purchase totals =	$668.24		$712.4532	$712.46	$712.45	$712.50