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	$175.85	11.123%	$195.4098	$195.41	$195.40	$195.40
Purchase #2	$196.90	3.404%	$203.6025	$203.60	$203.60	$203.60
Purchase #3	$27.60	12.462%	$31.0395	$31.04	$31.05	$31.00
Purchase #4	$49.51	10.506%	$54.7115	$54.71	$54.70	$54.70
Purchase #5	$35.84	13.251%	$40.5892	$40.59	$40.60	$40.60
Purchase #6	$209.58	6.205%	$222.5844	$222.58	$222.60	$222.60
Purchase #7	$5.96	13.637%	$6.7728	$6.77	$6.75	$6.80
7 purchase totals =	$701.24		$754.7097	$754.70	$754.70	$754.70