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	$64.26	13.447%	$72.901	$72.90	$72.90	$72.90
Purchase #2	$137.35	3.518%	$142.182	$142.18	$142.20	$142.20
Purchase #3	$220.93	5.358%	$232.7674	$232.77	$232.75	$232.80
Purchase #4	$235.42	11.820%	$263.2466	$263.25	$263.25	$263.20
Purchase #5	$162.34	3.853%	$168.595	$168.60	$168.60	$168.60
Purchase #6	$55.66	7.228%	$59.6831	$59.68	$59.70	$59.70
Purchase #7	$118.40	4.250%	$123.432	$123.43	$123.45	$123.40
7 purchase totals =	$994.36		$1,062.8071	$1,062.81	$1,062.85	$1,062.80