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	$41.72	4.799%	$43.7221	$43.72	$43.70	$43.70
Purchase #2	$180.33	10.700%	$199.6253	$199.63	$199.65	$199.60
Purchase #3	$94.91	9.509%	$103.935	$103.94	$103.95	$103.90
Purchase #4	$34.67	3.700%	$35.9528	$35.95	$35.95	$36.00
Purchase #5	$105.86	5.846%	$112.0486	$112.05	$112.05	$112.00
Purchase #6	$86.63	7.155%	$92.8284	$92.83	$92.85	$92.80
Purchase #7	$229.86	12.509%	$258.6132	$258.61	$258.60	$258.60
7 purchase totals =	$773.98		$846.7254	$846.73	$846.75	$846.60