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	$167.96	4.208%	$175.0278	$175.03	$175.05	$175.00
Purchase #2	$108.79	13.223%	$123.1753	$123.18	$123.20	$123.20
Purchase #3	$228.71	12.140%	$256.4754	$256.48	$256.50	$256.50
Purchase #4	$218.96	5.787%	$231.6312	$231.63	$231.65	$231.60
Purchase #5	$19.53	10.736%	$21.6267	$21.63	$21.65	$21.60
Purchase #6	$6.98	8.784%	$7.5931	$7.59	$7.60	$7.60
Purchase #7	$100.77	10.399%	$111.2491	$111.25	$111.25	$111.20
7 purchase totals =	$851.70		$926.7786	$926.79	$926.90	$926.70