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	$236.32	4.746%	$247.5357	$247.54	$247.55	$247.50
Purchase #2	$185.48	6.731%	$197.9647	$197.96	$197.95	$198.00
Purchase #3	$158.59	7.340%	$170.2305	$170.23	$170.25	$170.20
Purchase #4	$42.39	12.316%	$47.6108	$47.61	$47.60	$47.60
Purchase #5	$96.95	3.769%	$100.604	$100.60	$100.60	$100.60
Purchase #6	$131.77	4.653%	$137.9013	$137.90	$137.90	$137.90
Purchase #7	$159.45	3.367%	$164.8187	$164.82	$164.80	$164.80
7 purchase totals =	$1,010.95		$1,066.6657	$1,066.66	$1,066.65	$1,066.60