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	$61.63	6.547%	$65.6649	$65.66	$65.65	$65.70
Purchase #2	$50.67	6.352%	$53.8886	$53.89	$53.90	$53.90
Purchase #3	$33.66	7.492%	$36.1818	$36.18	$36.20	$36.20
Purchase #4	$243.73	4.269%	$254.1348	$254.13	$254.15	$254.10
Purchase #5	$209.27	8.280%	$226.5976	$226.60	$226.60	$226.60
Purchase #6	$172.34	10.846%	$191.032	$191.03	$191.05	$191.00
Purchase #7	$172.80	10.541%	$191.0148	$191.01	$191.00	$191.00
7 purchase totals =	$944.10		$1,018.5145	$1,018.50	$1,018.55	$1,018.50