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	$40.67	12.621%	$45.803	$45.80	$45.80	$45.80
Purchase #2	$54.80	7.778%	$59.0623	$59.06	$59.05	$59.10
Purchase #3	$61.25	12.106%	$68.6649	$68.66	$68.65	$68.70
Purchase #4	$104.69	3.448%	$108.2997	$108.30	$108.30	$108.30
Purchase #5	$106.93	7.118%	$114.5413	$114.54	$114.55	$114.50
Purchase #6	$238.72	9.605%	$261.6491	$261.65	$261.65	$261.60
Purchase #7	$244.52	4.555%	$255.6579	$255.66	$255.65	$255.70
7 purchase totals =	$851.58		$913.6782	$913.67	$913.65	$913.70