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	$85.79	10.348%	$94.6675	$94.67	$94.65	$94.70
Purchase #2	$165.90	11.576%	$185.1046	$185.10	$185.10	$185.10
Purchase #3	$97.85	7.625%	$105.3111	$105.31	$105.30	$105.30
Purchase #4	$79.43	7.695%	$85.5421	$85.54	$85.55	$85.50
Purchase #5	$38.76	8.774%	$42.1608	$42.16	$42.15	$42.20
Purchase #6	$134.69	10.426%	$148.7328	$148.73	$148.75	$148.70
Purchase #7	$75.40	13.356%	$85.4704	$85.47	$85.45	$85.50
7 purchase totals =	$677.82		$746.9893	$746.98	$746.95	$747.00