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	$85.75	5.814%	$90.7355	$90.74	$90.75	$90.70
Purchase #2	$172.41	11.738%	$192.6475	$192.65	$192.65	$192.60
Purchase #3	$195.56	9.411%	$213.9642	$213.96	$213.95	$214.00
Purchase #4	$228.93	5.437%	$241.3769	$241.38	$241.40	$241.40
Purchase #5	$101.27	8.166%	$109.5397	$109.54	$109.55	$109.50
Purchase #6	$105.54	12.281%	$118.5014	$118.50	$118.50	$118.50
Purchase #7	$204.85	10.204%	$225.7529	$225.75	$225.75	$225.80
7 purchase totals =	$1,094.31		$1,192.5181	$1,192.52	$1,192.55	$1,192.50