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	$26.90	7.235%	$28.8462	$28.85	$28.85	$28.80
Purchase #2	$99.98	7.508%	$107.4865	$107.49	$107.50	$107.50
Purchase #3	$70.31	13.610%	$79.8792	$79.88	$79.90	$79.90
Purchase #4	$78.83	8.361%	$85.421	$85.42	$85.40	$85.40
Purchase #5	$31.97	4.791%	$33.5017	$33.50	$33.50	$33.50
Purchase #6	$217.77	6.135%	$231.1302	$231.13	$231.15	$231.10
Purchase #7	$129.61	9.767%	$142.269	$142.27	$142.25	$142.30
7 purchase totals =	$655.37		$708.5338	$708.54	$708.55	$708.50