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	$170.84	11.416%	$190.3431	$190.34	$190.35	$190.30
Purchase #2	$246.67	10.219%	$271.8772	$271.88	$271.90	$271.90
Purchase #3	$224.98	11.582%	$251.0372	$251.04	$251.05	$251.00
Purchase #4	$70.38	3.572%	$72.894	$72.89	$72.90	$72.90
Purchase #5	$34.46	3.782%	$35.7633	$35.76	$35.75	$35.80
Purchase #6	$136.94	3.339%	$141.5124	$141.51	$141.50	$141.50
Purchase #7	$156.78	3.766%	$162.6843	$162.68	$162.70	$162.70
7 purchase totals =	$1,041.05		$1,126.1115	$1,126.10	$1,126.15	$1,126.10