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	$42.59	13.658%	$48.4069	$48.41	$48.40	$48.40
Purchase #2	$103.55	12.465%	$116.4575	$116.46	$116.45	$116.50
Purchase #3	$127.76	5.628%	$134.9503	$134.95	$134.95	$135.00
Purchase #4	$58.48	3.502%	$60.528	$60.53	$60.55	$60.50
Purchase #5	$226.89	6.541%	$241.7309	$241.73	$241.75	$241.70
Purchase #6	$162.30	10.848%	$179.9063	$179.91	$179.90	$179.90
Purchase #7	$61.39	10.110%	$67.5965	$67.60	$67.60	$67.60
7 purchase totals =	$782.96		$849.5764	$849.59	$849.60	$849.60