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	$215.51	11.657%	$240.632	$240.63	$240.65	$240.60
Purchase #2	$95.32	5.633%	$100.6894	$100.69	$100.70	$100.70
Purchase #3	$33.52	5.103%	$35.2305	$35.23	$35.25	$35.20
Purchase #4	$52.31	5.476%	$55.1745	$55.17	$55.15	$55.20
Purchase #5	$6.71	11.410%	$7.4756	$7.48	$7.50	$7.50
Purchase #6	$99.56	9.458%	$108.9764	$108.98	$109.00	$109.00
Purchase #7	$138.62	5.734%	$146.5685	$146.57	$146.55	$146.60
7 purchase totals =	$641.55		$694.7469	$694.75	$694.80	$694.80