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	$7.35	3.685%	$7.6208	$7.62	$7.60	$7.60
Purchase #2	$26.33	13.546%	$29.8967	$29.90	$29.90	$29.90
Purchase #3	$28.34	9.733%	$31.0983	$31.10	$31.10	$31.10
Purchase #4	$32.41	9.734%	$35.5648	$35.56	$35.55	$35.60
Purchase #5	$228.87	7.306%	$245.5912	$245.59	$245.60	$245.60
Purchase #6	$187.33	4.753%	$196.2338	$196.23	$196.25	$196.20
Purchase #7	$182.88	11.182%	$203.3296	$203.33	$203.35	$203.30
7 purchase totals =	$693.51		$749.3352	$749.33	$749.35	$749.30