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	$126.68	10.815%	$140.3804	$140.38	$140.40	$140.40
Purchase #2	$240.49	8.373%	$260.6262	$260.63	$260.65	$260.60
Purchase #3	$166.29	13.590%	$188.8888	$188.89	$188.90	$188.90
Purchase #4	$122.63	7.263%	$131.5366	$131.54	$131.55	$131.50
Purchase #5	$42.40	7.285%	$45.4888	$45.49	$45.50	$45.50
Purchase #6	$237.73	13.543%	$269.9258	$269.93	$269.95	$269.90
Purchase #7	$161.61	12.679%	$182.1005	$182.10	$182.10	$182.10
7 purchase totals =	$1,097.83		$1,218.9471	$1,218.96	$1,219.05	$1,218.90