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	$166.83	12.557%	$187.7788	$187.78	$187.80	$187.80
Purchase #2	$178.45	5.287%	$187.8847	$187.88	$187.90	$187.90
Purchase #3	$167.30	4.814%	$175.3538	$175.35	$175.35	$175.40
Purchase #4	$187.94	13.600%	$213.4998	$213.50	$213.50	$213.50
Purchase #5	$31.91	11.428%	$35.5567	$35.56	$35.55	$35.60
Purchase #6	$129.95	7.189%	$139.2921	$139.29	$139.30	$139.30
Purchase #7	$198.96	5.429%	$209.7615	$209.76	$209.75	$209.80
7 purchase totals =	$1,061.34		$1,149.1274	$1,149.12	$1,149.15	$1,149.30