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	$105.87	4.712%	$110.8586	$110.86	$110.85	$110.90
Purchase #2	$182.94	9.833%	$200.9285	$200.93	$200.95	$200.90
Purchase #3	$73.72	6.379%	$78.4226	$78.42	$78.40	$78.40
Purchase #4	$203.49	12.730%	$229.3943	$229.39	$229.40	$229.40
Purchase #5	$236.51	8.329%	$256.2089	$256.21	$256.20	$256.20
Purchase #6	$126.56	3.398%	$130.8605	$130.86	$130.85	$130.90
Purchase #7	$203.46	8.734%	$221.2302	$221.23	$221.25	$221.20
7 purchase totals =	$1,132.55		$1,227.9036	$1,227.90	$1,227.90	$1,227.90