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	$209.93	3.195%	$216.6373	$216.64	$216.65	$216.60
Purchase #2	$179.34	11.709%	$200.3389	$200.34	$200.35	$200.30
Purchase #3	$121.42	7.322%	$130.3104	$130.31	$130.30	$130.30
Purchase #4	$140.75	9.808%	$154.5548	$154.55	$154.55	$154.60
Purchase #5	$80.47	12.741%	$90.7227	$90.72	$90.70	$90.70
Purchase #6	$242.47	7.778%	$261.3293	$261.33	$261.35	$261.30
Purchase #7	$160.37	5.656%	$169.4405	$169.44	$169.45	$169.40
7 purchase totals =	$1,134.75		$1,223.3339	$1,223.33	$1,223.35	$1,223.20