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	$232.59	9.216%	$254.0255	$254.03	$254.05	$254.00
Purchase #2	$248.70	10.758%	$275.4551	$275.46	$275.45	$275.50
Purchase #3	$33.73	7.213%	$36.1629	$36.16	$36.15	$36.20
Purchase #4	$13.89	5.184%	$14.6101	$14.61	$14.60	$14.60
Purchase #5	$160.80	6.743%	$171.6427	$171.64	$171.65	$171.60
Purchase #6	$54.27	3.272%	$56.0457	$56.05	$56.05	$56.00
Purchase #7	$40.72	11.573%	$45.4325	$45.43	$45.45	$45.40
7 purchase totals =	$784.70		$853.3745	$853.38	$853.40	$853.30