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	$170.34	12.418%	$191.4928	$191.49	$191.50	$191.50
Purchase #2	$250.51	8.255%	$271.1896	$271.19	$271.20	$271.20
Purchase #3	$63.66	6.264%	$67.6477	$67.65	$67.65	$67.60
Purchase #4	$85.87	4.276%	$89.5418	$89.54	$89.55	$89.50
Purchase #5	$145.41	3.489%	$150.4834	$150.48	$150.50	$150.50
Purchase #6	$200.78	8.868%	$218.5852	$218.59	$218.60	$218.60
Purchase #7	$156.91	6.791%	$167.5658	$167.57	$167.55	$167.60
7 purchase totals =	$1,073.48		$1,156.5063	$1,156.51	$1,156.55	$1,156.50