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	$40.90	11.787%	$45.7209	$45.72	$45.70	$45.70
Purchase #2	$100.54	11.130%	$111.7301	$111.73	$111.75	$111.70
Purchase #3	$43.89	8.725%	$47.7194	$47.72	$47.70	$47.70
Purchase #4	$10.80	8.455%	$11.7131	$11.71	$11.70	$11.70
Purchase #5	$195.83	4.541%	$204.7226	$204.72	$204.70	$204.70
Purchase #6	$100.68	13.158%	$113.9275	$113.93	$113.95	$113.90
Purchase #7	$149.41	5.787%	$158.0564	$158.06	$158.05	$158.10
7 purchase totals =	$642.05		$693.5900	$693.59	$693.55	$693.50