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	$32.47	10.347%	$35.8297	$35.83	$35.85	$35.80
Purchase #2	$162.48	6.317%	$172.7439	$172.74	$172.75	$172.70
Purchase #3	$23.90	4.415%	$24.9552	$24.96	$24.95	$25.00
Purchase #4	$74.82	13.735%	$85.0965	$85.10	$85.10	$85.10
Purchase #5	$213.97	10.198%	$235.7907	$235.79	$235.80	$235.80
Purchase #6	$240.40	10.188%	$264.892	$264.89	$264.90	$264.90
Purchase #7	$45.29	13.456%	$51.3842	$51.38	$51.40	$51.40
7 purchase totals =	$793.33		$870.6922	$870.69	$870.75	$870.70