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	$137.26	8.443%	$148.8489	$148.85	$148.85	$148.80
Purchase #2	$43.40	9.637%	$47.5825	$47.58	$47.60	$47.60
Purchase #3	$235.59	3.534%	$243.9158	$243.92	$243.90	$243.90
Purchase #4	$250.64	6.314%	$266.4654	$266.47	$266.45	$266.50
Purchase #5	$216.53	3.732%	$224.6109	$224.61	$224.60	$224.60
Purchase #6	$75.37	13.375%	$85.4507	$85.45	$85.45	$85.50
Purchase #7	$43.81	13.589%	$49.7633	$49.76	$49.75	$49.80
7 purchase totals =	$1,002.60		$1,066.6375	$1,066.64	$1,066.60	$1,066.70