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	$10.48	12.296%	$11.7686	$11.77	$11.75	$11.80
Purchase #2	$32.73	12.336%	$36.7676	$36.77	$36.75	$36.80
Purchase #3	$78.88	9.597%	$86.4501	$86.45	$86.45	$86.50
Purchase #4	$184.45	6.475%	$196.3931	$196.39	$196.40	$196.40
Purchase #5	$148.25	11.828%	$165.785	$165.79	$165.80	$165.80
Purchase #6	$208.84	3.619%	$216.3979	$216.40	$216.40	$216.40
Purchase #7	$127.91	10.407%	$141.2216	$141.22	$141.20	$141.20
7 purchase totals =	$791.54		$854.7839	$854.79	$854.75	$854.90