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	$61.59	9.692%	$67.5593	$67.56	$67.55	$67.60
Purchase #2	$41.96	8.513%	$45.5321	$45.53	$45.55	$45.50
Purchase #3	$182.86	3.400%	$189.0772	$189.08	$189.10	$189.10
Purchase #4	$235.87	7.500%	$253.5603	$253.56	$253.55	$253.60
Purchase #5	$41.57	11.703%	$46.4349	$46.43	$46.45	$46.40
Purchase #6	$36.40	3.371%	$37.627	$37.63	$37.65	$37.60
Purchase #7	$111.94	3.285%	$115.6172	$115.62	$115.60	$115.60
7 purchase totals =	$712.19		$755.4080	$755.41	$755.45	$755.40