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	$106.73	10.340%	$117.7659	$117.77	$117.75	$117.80
Purchase #2	$235.64	7.819%	$254.0647	$254.06	$254.05	$254.10
Purchase #3	$10.97	8.591%	$11.9124	$11.91	$11.90	$11.90
Purchase #4	$96.75	13.554%	$109.8635	$109.86	$109.85	$109.90
Purchase #5	$56.48	4.812%	$59.1978	$59.20	$59.20	$59.20
Purchase #6	$91.81	4.480%	$95.9231	$95.92	$95.90	$95.90
Purchase #7	$37.35	3.174%	$38.5355	$38.54	$38.55	$38.50
7 purchase totals =	$635.73		$687.2629	$687.26	$687.20	$687.30