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	$189.32	5.841%	$200.3782	$200.38	$200.40	$200.40
Purchase #2	$234.50	4.720%	$245.5684	$245.57	$245.55	$245.60
Purchase #3	$85.53	12.753%	$96.4376	$96.44	$96.45	$96.40
Purchase #4	$132.96	5.577%	$140.3752	$140.38	$140.40	$140.40
Purchase #5	$244.57	4.314%	$255.1207	$255.12	$255.10	$255.10
Purchase #6	$184.43	7.715%	$198.6588	$198.66	$198.65	$198.70
Purchase #7	$216.45	10.195%	$238.5171	$238.52	$238.50	$238.50
7 purchase totals =	$1,287.76		$1,375.0560	$1,375.07	$1,375.05	$1,375.10