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	$23.41	10.503%	$25.8688	$25.87	$25.85	$25.90
Purchase #2	$65.45	11.696%	$73.105	$73.11	$73.10	$73.10
Purchase #3	$31.86	7.208%	$34.1565	$34.16	$34.15	$34.20
Purchase #4	$32.95	12.538%	$37.0813	$37.08	$37.10	$37.10
Purchase #5	$12.90	4.402%	$13.4679	$13.47	$13.45	$13.50
Purchase #6	$167.27	10.585%	$184.9755	$184.98	$185.00	$185.00
Purchase #7	$104.29	4.415%	$108.8944	$108.89	$108.90	$108.90
7 purchase totals =	$438.13		$477.5494	$477.56	$477.55	$477.70