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	$32.65	7.290%	$35.0302	$35.03	$35.05	$35.00
Purchase #2	$89.38	11.214%	$99.4031	$99.40	$99.40	$99.40
Purchase #3	$6.91	10.509%	$7.6362	$7.64	$7.65	$7.60
Purchase #4	$76.37	8.210%	$82.64	$82.64	$82.65	$82.60
Purchase #5	$154.61	10.619%	$171.028	$171.03	$171.05	$171.00
Purchase #6	$120.62	11.626%	$134.6433	$134.64	$134.65	$134.60
Purchase #7	$74.25	10.176%	$81.8057	$81.81	$81.80	$81.80
7 purchase totals =	$554.79		$612.1865	$612.19	$612.25	$612.00