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	$124.69	5.496%	$131.543	$131.54	$131.55	$131.50
Purchase #2	$162.57	6.778%	$173.589	$173.59	$173.60	$173.60
Purchase #3	$232.51	4.170%	$242.2057	$242.21	$242.20	$242.20
Purchase #4	$94.97	7.789%	$102.3672	$102.37	$102.35	$102.40
Purchase #5	$27.89	13.147%	$31.5567	$31.56	$31.55	$31.60
Purchase #6	$64.72	8.644%	$70.3144	$70.31	$70.30	$70.30
Purchase #7	$207.54	6.461%	$220.9492	$220.95	$220.95	$220.90
7 purchase totals =	$914.89		$972.5252	$972.53	$972.50	$972.50