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	$93.89	5.266%	$98.8342	$98.83	$98.85	$98.80
Purchase #2	$175.61	11.867%	$196.4496	$196.45	$196.45	$196.40
Purchase #3	$204.68	6.710%	$218.414	$218.41	$218.40	$218.40
Purchase #4	$219.68	12.565%	$247.2828	$247.28	$247.30	$247.30
Purchase #5	$133.45	5.523%	$140.8204	$140.82	$140.80	$140.80
Purchase #6	$14.55	8.722%	$15.8191	$15.82	$15.80	$15.80
Purchase #7	$94.38	7.376%	$101.3415	$101.34	$101.35	$101.30
7 purchase totals =	$936.24		$1,018.9616	$1,018.95	$1,018.95	$1,018.80