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	$106.52	12.522%	$119.8584	$119.86	$119.85	$119.90
Purchase #2	$84.98	5.735%	$89.8536	$89.85	$89.85	$89.90
Purchase #3	$175.88	3.281%	$181.6506	$181.65	$181.65	$181.70
Purchase #4	$40.32	10.389%	$44.5088	$44.51	$44.50	$44.50
Purchase #5	$81.53	12.864%	$92.018	$92.02	$92.00	$92.00
Purchase #6	$124.72	6.216%	$132.4726	$132.47	$132.45	$132.50
Purchase #7	$157.25	7.643%	$169.2686	$169.27	$169.25	$169.30
7 purchase totals =	$771.20		$829.6306	$829.63	$829.55	$829.80