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	$50.64	4.761%	$53.051	$53.05	$53.05	$53.10
Purchase #2	$221.69	4.256%	$231.1251	$231.13	$231.15	$231.10
Purchase #3	$128.82	13.166%	$145.7804	$145.78	$145.80	$145.80
Purchase #4	$32.84	9.868%	$36.0807	$36.08	$36.10	$36.10
Purchase #5	$138.89	6.673%	$148.1581	$148.16	$148.15	$148.20
Purchase #6	$30.88	3.240%	$31.8805	$31.88	$31.90	$31.90
Purchase #7	$60.27	6.302%	$64.0682	$64.07	$64.05	$64.10
7 purchase totals =	$664.03		$710.1440	$710.15	$710.20	$710.30