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	$152.41	9.129%	$166.3235	$166.32	$166.30	$166.30
Purchase #2	$172.74	7.305%	$185.3587	$185.36	$185.35	$185.40
Purchase #3	$29.50	3.437%	$30.5139	$30.51	$30.50	$30.50
Purchase #4	$246.57	3.455%	$255.089	$255.09	$255.10	$255.10
Purchase #5	$203.97	13.423%	$231.3489	$231.35	$231.35	$231.30
Purchase #6	$135.60	12.760%	$152.9026	$152.90	$152.90	$152.90
Purchase #7	$20.53	6.563%	$21.8774	$21.88	$21.90	$21.90
7 purchase totals =	$961.32		$1,043.4140	$1,043.41	$1,043.40	$1,043.40