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	$134.76	4.326%	$140.5897	$140.59	$140.60	$140.60
Purchase #2	$100.35	9.234%	$109.6163	$109.62	$109.60	$109.60
Purchase #3	$125.69	5.749%	$132.9159	$132.92	$132.90	$132.90
Purchase #4	$11.54	7.551%	$12.4114	$12.41	$12.40	$12.40
Purchase #5	$99.80	5.705%	$105.4936	$105.49	$105.50	$105.50
Purchase #6	$240.65	8.683%	$261.5456	$261.55	$261.55	$261.50
Purchase #7	$191.42	4.655%	$200.3306	$200.33	$200.35	$200.30
7 purchase totals =	$904.21		$962.9031	$962.91	$962.90	$962.80