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	$104.85	11.417%	$116.8207	$116.82	$116.80	$116.80
Purchase #2	$67.39	8.155%	$72.8857	$72.89	$72.90	$72.90
Purchase #3	$135.56	13.609%	$154.0084	$154.01	$154.00	$154.00
Purchase #4	$94.68	11.689%	$105.7471	$105.75	$105.75	$105.70
Purchase #5	$209.34	10.384%	$231.0779	$231.08	$231.10	$231.10
Purchase #6	$130.79	8.823%	$142.3296	$142.33	$142.35	$142.30
Purchase #7	$98.34	5.418%	$103.6681	$103.67	$103.65	$103.70
7 purchase totals =	$840.95		$926.5375	$926.55	$926.55	$926.50