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	$33.28	9.179%	$36.3348	$36.33	$36.35	$36.30
Purchase #2	$71.83	11.487%	$80.0811	$80.08	$80.10	$80.10
Purchase #3	$140.57	7.393%	$150.9623	$150.96	$150.95	$151.00
Purchase #4	$179.49	9.143%	$195.9008	$195.90	$195.90	$195.90
Purchase #5	$209.80	5.841%	$222.0544	$222.05	$222.05	$222.10
Purchase #6	$54.43	9.248%	$59.4637	$59.46	$59.45	$59.50
Purchase #7	$19.42	3.565%	$20.1123	$20.11	$20.10	$20.10
7 purchase totals =	$708.82		$764.9094	$764.89	$764.90	$765.00