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	$156.26	8.535%	$169.5968	$169.60	$169.60	$169.60
Purchase #2	$205.37	8.264%	$222.3418	$222.34	$222.35	$222.30
Purchase #3	$223.85	13.426%	$253.9041	$253.90	$253.90	$253.90
Purchase #4	$47.86	5.670%	$50.5737	$50.57	$50.55	$50.60
Purchase #5	$61.79	7.283%	$66.2902	$66.29	$66.30	$66.30
Purchase #6	$28.39	11.849%	$31.7539	$31.75	$31.75	$31.80
Purchase #7	$203.34	11.843%	$227.4216	$227.42	$227.40	$227.40
7 purchase totals =	$926.86		$1,021.8821	$1,021.87	$1,021.85	$1,021.90