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	$40.64	5.702%	$42.9573	$42.96	$42.95	$43.00
Purchase #2	$194.71	9.812%	$213.8149	$213.81	$213.80	$213.80
Purchase #3	$77.85	9.314%	$85.1009	$85.10	$85.10	$85.10
Purchase #4	$29.73	3.449%	$30.7554	$30.76	$30.75	$30.80
Purchase #5	$95.83	4.493%	$100.1356	$100.14	$100.15	$100.10
Purchase #6	$74.90	4.478%	$78.254	$78.25	$78.25	$78.30
Purchase #7	$229.66	4.771%	$240.6171	$240.62	$240.60	$240.60
7 purchase totals =	$743.32		$791.6352	$791.64	$791.60	$791.70