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	$190.37	13.333%	$215.752	$215.75	$215.75	$215.80
Purchase #2	$221.56	5.771%	$234.3462	$234.35	$234.35	$234.30
Purchase #3	$108.79	8.145%	$117.6509	$117.65	$117.65	$117.70
Purchase #4	$34.61	5.196%	$36.4083	$36.41	$36.40	$36.40
Purchase #5	$81.38	9.698%	$89.2722	$89.27	$89.25	$89.30
Purchase #6	$131.58	5.817%	$139.234	$139.23	$139.25	$139.20
Purchase #7	$104.68	4.656%	$109.5539	$109.55	$109.55	$109.60
7 purchase totals =	$872.97		$942.2175	$942.21	$942.20	$942.30