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	$102.69	13.764%	$116.8243	$116.82	$116.80	$116.80
Purchase #2	$147.34	4.872%	$154.5184	$154.52	$154.50	$154.50
Purchase #3	$213.33	7.577%	$229.494	$229.49	$229.50	$229.50
Purchase #4	$35.38	6.684%	$37.7448	$37.74	$37.75	$37.70
Purchase #5	$217.84	13.169%	$246.5273	$246.53	$246.55	$246.50
Purchase #6	$144.43	9.290%	$157.8475	$157.85	$157.85	$157.80
Purchase #7	$130.61	9.317%	$142.7789	$142.78	$142.80	$142.80
7 purchase totals =	$991.62		$1,085.7352	$1,085.73	$1,085.75	$1,085.60