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	$222.80	7.867%	$240.3277	$240.33	$240.35	$240.30
Purchase #2	$232.51	11.792%	$259.9276	$259.93	$259.95	$259.90
Purchase #3	$150.78	10.552%	$166.6903	$166.69	$166.70	$166.70
Purchase #4	$107.81	13.224%	$122.0668	$122.07	$122.05	$122.10
Purchase #5	$139.82	3.714%	$145.0129	$145.01	$145.00	$145.00
Purchase #6	$139.36	4.393%	$145.4821	$145.48	$145.50	$145.50
Purchase #7	$165.55	6.231%	$175.8654	$175.87	$175.85	$175.90
7 purchase totals =	$1,158.63		$1,255.3728	$1,255.38	$1,255.40	$1,255.40