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	$11.30	8.295%	$12.2373	$12.24	$12.25	$12.20
Purchase #2	$199.55	8.339%	$216.1905	$216.19	$216.20	$216.20
Purchase #3	$111.58	6.597%	$118.9409	$118.94	$118.95	$118.90
Purchase #4	$185.93	3.199%	$191.8779	$191.88	$191.90	$191.90
Purchase #5	$92.59	13.769%	$105.3387	$105.34	$105.35	$105.30
Purchase #6	$130.54	8.597%	$141.7625	$141.76	$141.75	$141.80
Purchase #7	$132.41	4.839%	$138.8173	$138.82	$138.80	$138.80
7 purchase totals =	$863.90		$925.1651	$925.17	$925.20	$925.10