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	$206.51	11.237%	$229.7155	$229.72	$229.70	$229.70
Purchase #2	$180.56	3.534%	$186.941	$186.94	$186.95	$186.90
Purchase #3	$148.62	13.627%	$168.8724	$168.87	$168.85	$168.90
Purchase #4	$20.33	6.695%	$21.6911	$21.69	$21.70	$21.70
Purchase #5	$117.38	11.751%	$131.1733	$131.17	$131.15	$131.20
Purchase #6	$246.75	12.203%	$276.8609	$276.86	$276.85	$276.90
Purchase #7	$148.83	12.500%	$167.4338	$167.43	$167.45	$167.40
7 purchase totals =	$1,068.98		$1,182.6880	$1,182.68	$1,182.65	$1,182.70