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	$138.58	4.293%	$144.5292	$144.53	$144.55	$144.50
Purchase #2	$162.36	3.548%	$168.1205	$168.12	$168.10	$168.10
Purchase #3	$29.71	5.251%	$31.2701	$31.27	$31.25	$31.30
Purchase #4	$28.70	11.846%	$32.0998	$32.10	$32.10	$32.10
Purchase #5	$222.94	8.197%	$241.2144	$241.21	$241.20	$241.20
Purchase #6	$184.53	6.691%	$196.8769	$196.88	$196.90	$196.90
Purchase #7	$87.32	4.302%	$91.0765	$91.08	$91.10	$91.10
7 purchase totals =	$854.14		$905.1874	$905.19	$905.20	$905.20