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	$58.48	12.390%	$65.7257	$65.73	$65.75	$65.70
Purchase #2	$50.45	13.316%	$57.1679	$57.17	$57.15	$57.20
Purchase #3	$169.86	11.444%	$189.2988	$189.30	$189.30	$189.30
Purchase #4	$183.47	7.115%	$196.5239	$196.52	$196.50	$196.50
Purchase #5	$164.88	3.793%	$171.1339	$171.13	$171.15	$171.10
Purchase #6	$64.59	11.387%	$71.9449	$71.94	$71.95	$71.90
Purchase #7	$5.38	8.462%	$5.8353	$5.84	$5.85	$5.80
7 purchase totals =	$697.11		$757.6304	$757.63	$757.65	$757.50