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	$148.83	13.215%	$168.4979	$168.50	$168.50	$168.50
Purchase #2	$30.61	12.368%	$34.3958	$34.40	$34.40	$34.40
Purchase #3	$26.25	8.206%	$28.4041	$28.40	$28.40	$28.40
Purchase #4	$89.77	11.625%	$100.2058	$100.21	$100.20	$100.20
Purchase #5	$100.33	13.153%	$113.5264	$113.53	$113.55	$113.50
Purchase #6	$136.31	11.826%	$152.43	$152.43	$152.45	$152.40
Purchase #7	$179.80	10.832%	$199.2759	$199.28	$199.30	$199.30
7 purchase totals =	$711.90		$796.7359	$796.75	$796.80	$796.70