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	$34.55	7.665%	$37.1983	$37.20	$37.20	$37.20
Purchase #2	$40.25	4.783%	$42.1752	$42.18	$42.20	$42.20
Purchase #3	$133.31	12.690%	$150.227	$150.23	$150.25	$150.20
Purchase #4	$106.28	7.529%	$114.2818	$114.28	$114.30	$114.30
Purchase #5	$46.97	13.852%	$53.4763	$53.48	$53.50	$53.50
Purchase #6	$179.72	10.526%	$198.6373	$198.64	$198.65	$198.60
Purchase #7	$214.72	3.694%	$222.6518	$222.65	$222.65	$222.70
7 purchase totals =	$755.80		$818.6477	$818.66	$818.75	$818.70