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	$17.97	8.794%	$19.5503	$19.55	$19.55	$19.60
Purchase #2	$119.63	9.485%	$130.9769	$130.98	$131.00	$131.00
Purchase #3	$11.25	4.474%	$11.7533	$11.75	$11.75	$11.80
Purchase #4	$177.80	7.120%	$190.4594	$190.46	$190.45	$190.50
Purchase #5	$56.93	3.680%	$59.025	$59.03	$59.05	$59.00
Purchase #6	$171.72	3.307%	$177.3988	$177.40	$177.40	$177.40
Purchase #7	$145.56	4.340%	$151.8773	$151.88	$151.90	$151.90
7 purchase totals =	$700.86		$741.0410	$741.05	$741.10	$741.20