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	$191.82	8.521%	$208.165	$208.17	$208.15	$208.20
Purchase #2	$57.48	11.179%	$63.9057	$63.91	$63.90	$63.90
Purchase #3	$36.78	11.228%	$40.9097	$40.91	$40.90	$40.90
Purchase #4	$201.33	12.534%	$226.5647	$226.56	$226.55	$226.60
Purchase #5	$127.76	10.816%	$141.5785	$141.58	$141.60	$141.60
Purchase #6	$155.88	10.228%	$171.8234	$171.82	$171.80	$171.80
Purchase #7	$51.69	7.432%	$55.5316	$55.53	$55.55	$55.50
7 purchase totals =	$822.74		$908.4786	$908.48	$908.45	$908.50