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	$164.25	10.314%	$181.1907	$181.19	$181.20	$181.20
Purchase #2	$36.58	3.143%	$37.7297	$37.73	$37.75	$37.70
Purchase #3	$49.27	5.290%	$51.8764	$51.88	$51.90	$51.90
Purchase #4	$160.48	5.787%	$169.767	$169.77	$169.75	$169.80
Purchase #5	$209.35	6.389%	$222.7254	$222.73	$222.75	$222.70
Purchase #6	$51.78	5.386%	$54.5689	$54.57	$54.55	$54.60
Purchase #7	$202.56	9.507%	$221.8174	$221.82	$221.80	$221.80
7 purchase totals =	$874.27		$939.6755	$939.69	$939.70	$939.70