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	$202.31	7.639%	$217.7645	$217.76	$217.75	$217.80
Purchase #2	$199.52	12.227%	$223.9153	$223.92	$223.90	$223.90
Purchase #3	$144.54	8.645%	$157.0355	$157.04	$157.05	$157.00
Purchase #4	$67.31	6.646%	$71.7834	$71.78	$71.80	$71.80
Purchase #5	$121.89	6.496%	$129.808	$129.81	$129.80	$129.80
Purchase #6	$145.59	7.213%	$156.0914	$156.09	$156.10	$156.10
Purchase #7	$174.83	6.343%	$185.9195	$185.92	$185.90	$185.90
7 purchase totals =	$1,055.99		$1,142.3176	$1,142.32	$1,142.30	$1,142.30