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	$243.37	5.348%	$256.3854	$256.39	$256.40	$256.40
Purchase #2	$100.49	11.738%	$112.2855	$112.29	$112.30	$112.30
Purchase #3	$174.43	9.771%	$191.4736	$191.47	$191.45	$191.50
Purchase #4	$151.79	9.590%	$166.3467	$166.35	$166.35	$166.30
Purchase #5	$58.44	4.185%	$60.8857	$60.89	$60.90	$60.90
Purchase #6	$38.84	11.327%	$43.2394	$43.24	$43.25	$43.20
Purchase #7	$185.64	9.777%	$203.79	$203.79	$203.80	$203.80
7 purchase totals =	$953.00		$1,034.4063	$1,034.42	$1,034.45	$1,034.40