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	$62.83	6.670%	$67.0208	$67.02	$67.00	$67.00
Purchase #2	$38.61	10.466%	$42.6509	$42.65	$42.65	$42.70
Purchase #3	$74.91	5.817%	$79.2675	$79.27	$79.25	$79.30
Purchase #4	$49.53	12.530%	$55.7361	$55.74	$55.75	$55.70
Purchase #5	$49.91	6.727%	$53.2674	$53.27	$53.25	$53.30
Purchase #6	$121.30	3.533%	$125.5855	$125.59	$125.60	$125.60
Purchase #7	$10.42	5.640%	$11.0077	$11.01	$11.00	$11.00
7 purchase totals =	$407.51		$434.5359	$434.55	$434.50	$434.60