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	$203.91	10.319%	$224.9515	$224.95	$224.95	$225.00
Purchase #2	$245.39	11.603%	$273.8626	$273.86	$273.85	$273.90
Purchase #3	$183.86	3.829%	$190.9	$190.90	$190.90	$190.90
Purchase #4	$28.75	12.665%	$32.3912	$32.39	$32.40	$32.40
Purchase #5	$93.79	6.830%	$100.1959	$100.20	$100.20	$100.20
Purchase #6	$168.47	8.228%	$182.3317	$182.33	$182.35	$182.30
Purchase #7	$113.61	4.250%	$118.4384	$118.44	$118.45	$118.40
7 purchase totals =	$1,037.78		$1,123.0713	$1,123.07	$1,123.10	$1,123.10