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	$245.30	4.148%	$255.475	$255.48	$255.50	$255.50
Purchase #2	$209.42	8.141%	$226.4689	$226.47	$226.45	$226.50
Purchase #3	$45.33	10.536%	$50.106	$50.11	$50.10	$50.10
Purchase #4	$226.94	13.256%	$257.0232	$257.02	$257.00	$257.00
Purchase #5	$191.54	4.822%	$200.7761	$200.78	$200.80	$200.80
Purchase #6	$5.87	7.605%	$6.3164	$6.32	$6.30	$6.30
Purchase #7	$159.83	7.817%	$172.3239	$172.32	$172.30	$172.30
7 purchase totals =	$1,084.23		$1,168.4895	$1,168.50	$1,168.45	$1,168.50