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	$133.52	9.232%	$145.8466	$145.85	$145.85	$145.80
Purchase #2	$170.65	9.309%	$186.5358	$186.54	$186.55	$186.50
Purchase #3	$146.45	13.505%	$166.2281	$166.23	$166.25	$166.20
Purchase #4	$10.86	12.365%	$12.2028	$12.20	$12.20	$12.20
Purchase #5	$178.88	7.493%	$192.2835	$192.28	$192.30	$192.30
Purchase #6	$178.25	10.371%	$196.7363	$196.74	$196.75	$196.70
Purchase #7	$134.89	8.532%	$146.3988	$146.40	$146.40	$146.40
7 purchase totals =	$953.50		$1,046.2319	$1,046.24	$1,046.30	$1,046.10