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	$143.47	11.598%	$160.1097	$160.11	$160.10	$160.10
Purchase #2	$205.59	9.853%	$225.8468	$225.85	$225.85	$225.80
Purchase #3	$86.28	7.249%	$92.5344	$92.53	$92.55	$92.50
Purchase #4	$89.39	5.737%	$94.5183	$94.52	$94.50	$94.50
Purchase #5	$142.69	9.342%	$156.0201	$156.02	$156.00	$156.00
Purchase #6	$65.76	9.681%	$72.1262	$72.13	$72.15	$72.10
Purchase #7	$243.76	7.838%	$262.8659	$262.87	$262.85	$262.90
7 purchase totals =	$976.94		$1,064.0214	$1,064.03	$1,064.00	$1,063.90