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	$143.59	4.358%	$149.8477	$149.85	$149.85	$149.80
Purchase #2	$216.52	7.834%	$233.4822	$233.48	$233.50	$233.50
Purchase #3	$20.96	4.255%	$21.8518	$21.85	$21.85	$21.90
Purchase #4	$187.64	7.511%	$201.7336	$201.73	$201.75	$201.70
Purchase #5	$158.43	5.373%	$166.9424	$166.94	$166.95	$166.90
Purchase #6	$39.53	6.870%	$42.2457	$42.25	$42.25	$42.20
Purchase #7	$19.89	6.798%	$21.2421	$21.24	$21.25	$21.20
7 purchase totals =	$786.56		$837.3455	$837.34	$837.40	$837.20