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	$68.87	13.720%	$78.319	$78.32	$78.30	$78.30
Purchase #2	$104.43	6.514%	$111.2326	$111.23	$111.25	$111.20
Purchase #3	$114.25	3.149%	$117.8477	$117.85	$117.85	$117.80
Purchase #4	$234.82	4.475%	$245.3282	$245.33	$245.35	$245.30
Purchase #5	$38.78	8.628%	$42.1259	$42.13	$42.15	$42.10
Purchase #6	$103.59	5.433%	$109.218	$109.22	$109.20	$109.20
Purchase #7	$183.61	10.259%	$202.4465	$202.45	$202.45	$202.40
7 purchase totals =	$848.35		$906.5179	$906.53	$906.55	$906.30