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	$135.75	7.429%	$145.8349	$145.83	$145.85	$145.80
Purchase #2	$156.50	7.825%	$168.7461	$168.75	$168.75	$168.70
Purchase #3	$101.64	9.240%	$111.0315	$111.03	$111.05	$111.00
Purchase #4	$199.64	8.107%	$215.8248	$215.82	$215.80	$215.80
Purchase #5	$137.32	11.380%	$152.947	$152.95	$152.95	$152.90
Purchase #6	$247.79	4.736%	$259.5253	$259.53	$259.55	$259.50
Purchase #7	$223.68	3.251%	$230.9518	$230.95	$230.95	$231.00
7 purchase totals =	$1,202.32		$1,284.8614	$1,284.86	$1,284.90	$1,284.70