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	$143.90	5.460%	$151.7569	$151.76	$151.75	$151.80
Purchase #2	$99.43	12.582%	$111.9403	$111.94	$111.95	$111.90
Purchase #3	$43.79	6.611%	$46.685	$46.69	$46.70	$46.70
Purchase #4	$202.56	12.187%	$227.246	$227.25	$227.25	$227.20
Purchase #5	$189.26	7.125%	$202.7448	$202.74	$202.75	$202.70
Purchase #6	$143.72	9.161%	$156.8862	$156.89	$156.90	$156.90
Purchase #7	$147.78	3.222%	$152.5415	$152.54	$152.55	$152.50
7 purchase totals =	$970.44		$1,049.8007	$1,049.81	$1,049.85	$1,049.70