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	$43.67	3.128%	$45.036	$45.04	$45.05	$45.00
Purchase #2	$49.77	11.273%	$55.3806	$55.38	$55.40	$55.40
Purchase #3	$218.38	11.518%	$243.533	$243.53	$243.55	$243.50
Purchase #4	$67.34	5.450%	$71.01	$71.01	$71.00	$71.00
Purchase #5	$6.55	4.270%	$6.8297	$6.83	$6.85	$6.80
Purchase #6	$170.53	5.580%	$180.0456	$180.05	$180.05	$180.00
Purchase #7	$193.55	3.161%	$199.6681	$199.67	$199.65	$199.70
7 purchase totals =	$749.79		$801.5030	$801.51	$801.55	$801.40