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	$228.38	3.708%	$236.8483	$236.85	$236.85	$236.80
Purchase #2	$100.61	7.500%	$108.1558	$108.16	$108.15	$108.20
Purchase #3	$110.91	7.761%	$119.5177	$119.52	$119.50	$119.50
Purchase #4	$159.78	4.705%	$167.2976	$167.30	$167.30	$167.30
Purchase #5	$136.64	12.388%	$153.567	$153.57	$153.55	$153.60
Purchase #6	$172.54	8.482%	$187.1748	$187.17	$187.15	$187.20
Purchase #7	$112.55	12.294%	$126.3869	$126.39	$126.40	$126.40
7 purchase totals =	$1,021.41		$1,098.9481	$1,098.96	$1,098.90	$1,099.00