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	$136.95	8.671%	$148.8249	$148.82	$148.80	$148.80
Purchase #2	$79.56	3.115%	$82.0383	$82.04	$82.05	$82.00
Purchase #3	$35.28	6.609%	$37.6117	$37.61	$37.60	$37.60
Purchase #4	$153.96	10.149%	$169.5854	$169.59	$169.60	$169.60
Purchase #5	$94.83	6.517%	$101.0101	$101.01	$101.00	$101.00
Purchase #6	$126.46	8.862%	$137.6669	$137.67	$137.65	$137.70
Purchase #7	$27.82	11.604%	$31.0482	$31.05	$31.05	$31.00
7 purchase totals =	$654.86		$707.7855	$707.79	$707.75	$707.70