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	$196.72	9.327%	$215.0681	$215.07	$215.05	$215.10
Purchase #2	$191.89	12.468%	$215.8148	$215.81	$215.80	$215.80
Purchase #3	$215.34	9.671%	$236.1655	$236.17	$236.15	$236.20
Purchase #4	$60.31	10.250%	$66.4918	$66.49	$66.50	$66.50
Purchase #5	$231.43	13.740%	$263.2285	$263.23	$263.25	$263.20
Purchase #6	$222.67	13.805%	$253.4096	$253.41	$253.40	$253.40
Purchase #7	$109.76	7.241%	$117.7077	$117.71	$117.70	$117.70
7 purchase totals =	$1,228.12		$1,367.8860	$1,367.89	$1,367.85	$1,367.90