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	$135.83	13.705%	$154.4455	$154.45	$154.45	$154.40
Purchase #2	$26.61	4.683%	$27.8561	$27.86	$27.85	$27.90
Purchase #3	$89.74	13.770%	$102.0972	$102.10	$102.10	$102.10
Purchase #4	$98.94	6.616%	$105.4859	$105.49	$105.50	$105.50
Purchase #5	$87.84	7.189%	$94.1548	$94.15	$94.15	$94.20
Purchase #6	$203.46	6.597%	$216.8823	$216.88	$216.90	$216.90
Purchase #7	$211.40	7.494%	$227.2423	$227.24	$227.25	$227.20
7 purchase totals =	$853.82		$928.1641	$928.17	$928.20	$928.20