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	$203.30	3.574%	$210.5659	$210.57	$210.55	$210.60
Purchase #2	$88.52	11.713%	$98.8883	$98.89	$98.90	$98.90
Purchase #3	$99.33	10.137%	$109.3991	$109.40	$109.40	$109.40
Purchase #4	$157.34	10.417%	$173.7301	$173.73	$173.75	$173.70
Purchase #5	$237.35	7.439%	$255.0065	$255.01	$255.00	$255.00
Purchase #6	$65.66	4.337%	$68.5077	$68.51	$68.50	$68.50
Purchase #7	$227.69	4.483%	$237.8973	$237.90	$237.90	$237.90
7 purchase totals =	$1,079.19		$1,153.9949	$1,154.01	$1,154.00	$1,154.00