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	$80.36	6.683%	$85.7305	$85.73	$85.75	$85.70
Purchase #2	$58.43	10.811%	$64.7469	$64.75	$64.75	$64.70
Purchase #3	$7.80	13.363%	$8.8423	$8.84	$8.85	$8.80
Purchase #4	$85.70	10.658%	$94.8339	$94.83	$94.85	$94.80
Purchase #5	$61.72	5.674%	$65.222	$65.22	$65.20	$65.20
Purchase #6	$130.77	9.800%	$143.5855	$143.59	$143.60	$143.60
Purchase #7	$27.62	8.108%	$29.8594	$29.86	$29.85	$29.90
7 purchase totals =	$452.40		$492.8205	$492.82	$492.85	$492.70