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	$132.72	5.821%	$140.4456	$140.45	$140.45	$140.40
Purchase #2	$242.91	8.584%	$263.7614	$263.76	$263.75	$263.80
Purchase #3	$32.65	5.515%	$34.4506	$34.45	$34.45	$34.50
Purchase #4	$138.46	12.320%	$155.5183	$155.52	$155.50	$155.50
Purchase #5	$133.89	13.604%	$152.1044	$152.10	$152.10	$152.10
Purchase #6	$39.28	3.729%	$40.7448	$40.74	$40.75	$40.70
Purchase #7	$136.68	13.626%	$155.304	$155.30	$155.30	$155.30
7 purchase totals =	$856.59		$942.3291	$942.32	$942.30	$942.30