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	$145.61	7.501%	$156.5322	$156.53	$156.55	$156.50
Purchase #2	$98.47	3.389%	$101.8071	$101.81	$101.80	$101.80
Purchase #3	$162.60	13.271%	$184.1786	$184.18	$184.20	$184.20
Purchase #4	$64.28	4.278%	$67.0299	$67.03	$67.05	$67.00
Purchase #5	$57.96	8.544%	$62.9121	$62.91	$62.90	$62.90
Purchase #6	$9.98	10.465%	$11.0244	$11.02	$11.00	$11.00
Purchase #7	$102.43	13.763%	$116.5274	$116.53	$116.55	$116.50
7 purchase totals =	$641.33		$700.0117	$700.01	$700.05	$699.90