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	$140.61	8.776%	$152.9499	$152.95	$152.95	$152.90
Purchase #2	$210.55	5.618%	$222.3787	$222.38	$222.40	$222.40
Purchase #3	$111.41	7.151%	$119.3769	$119.38	$119.40	$119.40
Purchase #4	$61.73	3.251%	$63.7368	$63.74	$63.75	$63.70
Purchase #5	$235.57	12.246%	$264.4179	$264.42	$264.40	$264.40
Purchase #6	$55.89	7.866%	$60.2863	$60.29	$60.30	$60.30
Purchase #7	$116.86	13.832%	$133.0241	$133.02	$133.00	$133.00
7 purchase totals =	$932.62		$1,016.1706	$1,016.18	$1,016.20	$1,016.10