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	$112.56	12.865%	$127.0408	$127.04	$127.05	$127.00
Purchase #2	$213.52	8.402%	$231.46	$231.46	$231.45	$231.50
Purchase #3	$240.46	10.576%	$265.891	$265.89	$265.90	$265.90
Purchase #4	$11.46	4.262%	$11.9484	$11.95	$11.95	$11.90
Purchase #5	$134.45	5.171%	$141.4024	$141.40	$141.40	$141.40
Purchase #6	$244.58	11.718%	$273.2399	$273.24	$273.25	$273.20
Purchase #7	$195.53	7.708%	$210.6015	$210.60	$210.60	$210.60
7 purchase totals =	$1,152.56		$1,261.5840	$1,261.58	$1,261.60	$1,261.50