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	$226.92	8.294%	$245.7407	$245.74	$245.75	$245.70
Purchase #2	$101.66	9.641%	$111.461	$111.46	$111.45	$111.50
Purchase #3	$55.69	6.411%	$59.2603	$59.26	$59.25	$59.30
Purchase #4	$34.28	3.655%	$35.5329	$35.53	$35.55	$35.50
Purchase #5	$140.38	3.201%	$144.8736	$144.87	$144.85	$144.90
Purchase #6	$180.33	5.778%	$190.7495	$190.75	$190.75	$190.70
Purchase #7	$190.71	6.827%	$203.7298	$203.73	$203.75	$203.70
7 purchase totals =	$929.97		$991.3478	$991.34	$991.35	$991.30