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	$89.59	6.556%	$95.4635	$95.46	$95.45	$95.50
Purchase #2	$192.54	11.461%	$214.607	$214.61	$214.60	$214.60
Purchase #3	$111.81	5.665%	$118.144	$118.14	$118.15	$118.10
Purchase #4	$228.83	9.405%	$250.3515	$250.35	$250.35	$250.40
Purchase #5	$242.60	6.729%	$258.9246	$258.92	$258.90	$258.90
Purchase #6	$7.61	4.280%	$7.9357	$7.94	$7.95	$7.90
Purchase #7	$153.79	10.115%	$169.3459	$169.35	$169.35	$169.30
7 purchase totals =	$1,026.77		$1,114.7722	$1,114.77	$1,114.75	$1,114.70