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	$197.98	8.476%	$214.7608	$214.76	$214.75	$214.80
Purchase #2	$185.90	3.365%	$192.1555	$192.16	$192.15	$192.20
Purchase #3	$72.56	13.754%	$82.5399	$82.54	$82.55	$82.50
Purchase #4	$28.84	12.419%	$32.4216	$32.42	$32.40	$32.40
Purchase #5	$76.28	5.631%	$80.5753	$80.58	$80.60	$80.60
Purchase #6	$206.37	9.149%	$225.2508	$225.25	$225.25	$225.30
Purchase #7	$223.67	12.113%	$250.7631	$250.76	$250.75	$250.80
7 purchase totals =	$991.60		$1,078.4670	$1,078.47	$1,078.45	$1,078.60