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	$96.69	11.770%	$108.0704	$108.07	$108.05	$108.10
Purchase #2	$180.32	6.753%	$192.497	$192.50	$192.50	$192.50
Purchase #3	$167.96	10.467%	$185.5404	$185.54	$185.55	$185.50
Purchase #4	$115.57	11.737%	$129.1345	$129.13	$129.15	$129.10
Purchase #5	$163.34	5.743%	$172.7206	$172.72	$172.70	$172.70
Purchase #6	$125.50	8.261%	$135.8676	$135.87	$135.85	$135.90
Purchase #7	$83.93	7.294%	$90.0519	$90.05	$90.05	$90.10
7 purchase totals =	$933.31		$1,013.8824	$1,013.88	$1,013.85	$1,013.90