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	$82.77	8.679%	$89.9536	$89.95	$89.95	$90.00
Purchase #2	$210.65	4.867%	$220.9023	$220.90	$220.90	$220.90
Purchase #3	$92.93	3.284%	$95.9818	$95.98	$96.00	$96.00
Purchase #4	$213.55	13.544%	$242.4732	$242.47	$242.45	$242.50
Purchase #5	$212.28	13.771%	$241.5131	$241.51	$241.50	$241.50
Purchase #6	$28.41	10.569%	$31.4127	$31.41	$31.40	$31.40
Purchase #7	$163.85	7.244%	$175.7193	$175.72	$175.70	$175.70
7 purchase totals =	$1,004.44		$1,097.9560	$1,097.94	$1,097.90	$1,098.00