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	$245.88	5.502%	$259.4083	$259.41	$259.40	$259.40
Purchase #2	$244.92	6.735%	$261.4154	$261.42	$261.40	$261.40
Purchase #3	$48.66	13.834%	$55.3916	$55.39	$55.40	$55.40
Purchase #4	$217.47	13.674%	$247.2068	$247.21	$247.20	$247.20
Purchase #5	$89.31	12.380%	$100.3666	$100.37	$100.35	$100.40
Purchase #6	$52.33	12.763%	$59.0089	$59.01	$59.00	$59.00
Purchase #7	$137.44	7.660%	$147.9679	$147.97	$147.95	$148.00
7 purchase totals =	$1,036.01		$1,130.7655	$1,130.78	$1,130.70	$1,130.80