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	$236.62	13.433%	$268.4052	$268.41	$268.40	$268.40
Purchase #2	$40.54	6.462%	$43.1597	$43.16	$43.15	$43.20
Purchase #3	$147.57	4.385%	$154.0409	$154.04	$154.05	$154.00
Purchase #4	$47.38	9.439%	$51.8522	$51.85	$51.85	$51.90
Purchase #5	$212.72	11.604%	$237.404	$237.40	$237.40	$237.40
Purchase #6	$140.35	8.597%	$152.4159	$152.42	$152.40	$152.40
Purchase #7	$141.76	6.862%	$151.4876	$151.49	$151.50	$151.50
7 purchase totals =	$966.94		$1,058.7655	$1,058.77	$1,058.75	$1,058.80