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	$92.56	7.333%	$99.3474	$99.35	$99.35	$99.30
Purchase #2	$182.72	13.538%	$207.4566	$207.46	$207.45	$207.50
Purchase #3	$83.96	4.131%	$87.4284	$87.43	$87.45	$87.40
Purchase #4	$247.35	9.718%	$271.3875	$271.39	$271.40	$271.40
Purchase #5	$53.49	7.769%	$57.6456	$57.65	$57.65	$57.60
Purchase #6	$27.87	13.471%	$31.6244	$31.62	$31.60	$31.60
Purchase #7	$17.77	5.193%	$18.6928	$18.69	$18.70	$18.70
7 purchase totals =	$705.72		$773.5827	$773.59	$773.60	$773.50