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	$71.99	6.360%	$76.5686	$76.57	$76.55	$76.60
Purchase #2	$210.35	13.775%	$239.3257	$239.33	$239.35	$239.30
Purchase #3	$143.96	5.644%	$152.0851	$152.09	$152.10	$152.10
Purchase #4	$54.77	9.162%	$59.788	$59.79	$59.80	$59.80
Purchase #5	$60.30	3.561%	$62.4473	$62.45	$62.45	$62.40
Purchase #6	$127.82	11.425%	$142.4234	$142.42	$142.40	$142.40
Purchase #7	$171.50	12.503%	$192.9426	$192.94	$192.95	$192.90
7 purchase totals =	$840.69		$925.5807	$925.59	$925.60	$925.50