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	$215.92	11.564%	$240.889	$240.89	$240.90	$240.90
Purchase #2	$40.39	6.112%	$42.8586	$42.86	$42.85	$42.90
Purchase #3	$32.53	9.658%	$35.6717	$35.67	$35.65	$35.70
Purchase #4	$80.74	11.833%	$90.294	$90.29	$90.30	$90.30
Purchase #5	$173.57	11.132%	$192.8918	$192.89	$192.90	$192.90
Purchase #6	$247.84	6.824%	$264.7526	$264.75	$264.75	$264.80
Purchase #7	$84.99	6.123%	$90.1939	$90.19	$90.20	$90.20
7 purchase totals =	$875.98		$957.5516	$957.54	$957.55	$957.70