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	$74.93	7.250%	$80.3624	$80.36	$80.35	$80.40
Purchase #2	$103.59	7.327%	$111.18	$111.18	$111.20	$111.20
Purchase #3	$116.75	11.288%	$129.9287	$129.93	$129.95	$129.90
Purchase #4	$12.44	8.299%	$13.4724	$13.47	$13.45	$13.50
Purchase #5	$58.35	11.542%	$65.0848	$65.08	$65.10	$65.10
Purchase #6	$194.37	5.855%	$205.7504	$205.75	$205.75	$205.80
Purchase #7	$56.93	4.746%	$59.6319	$59.63	$59.65	$59.60
7 purchase totals =	$617.36		$665.4106	$665.40	$665.45	$665.50