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	$195.96	11.566%	$218.6247	$218.62	$218.60	$218.60
Purchase #2	$216.54	12.243%	$243.051	$243.05	$243.05	$243.10
Purchase #3	$26.93	12.452%	$30.2833	$30.28	$30.30	$30.30
Purchase #4	$226.89	12.331%	$254.8678	$254.87	$254.85	$254.90
Purchase #5	$34.29	13.545%	$38.9346	$38.93	$38.95	$38.90
Purchase #6	$74.38	9.513%	$81.4558	$81.46	$81.45	$81.50
Purchase #7	$142.41	7.154%	$152.598	$152.60	$152.60	$152.60
7 purchase totals =	$917.40		$1,019.8152	$1,019.81	$1,019.80	$1,019.90