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	$125.58	12.382%	$141.1293	$141.13	$141.15	$141.10
Purchase #2	$98.75	13.847%	$112.4239	$112.42	$112.40	$112.40
Purchase #3	$175.38	6.250%	$186.3413	$186.34	$186.35	$186.30
Purchase #4	$8.43	5.828%	$8.9213	$8.92	$8.90	$8.90
Purchase #5	$42.45	9.331%	$46.411	$46.41	$46.40	$46.40
Purchase #6	$20.91	4.189%	$21.7859	$21.79	$21.80	$21.80
Purchase #7	$141.66	7.705%	$152.5749	$152.57	$152.55	$152.60
7 purchase totals =	$613.16		$669.5876	$669.58	$669.55	$669.50