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	$203.61	7.823%	$219.5384	$219.54	$219.55	$219.50
Purchase #2	$47.81	13.106%	$54.076	$54.08	$54.10	$54.10
Purchase #3	$71.26	9.703%	$78.1744	$78.17	$78.15	$78.20
Purchase #4	$174.61	10.455%	$192.8655	$192.87	$192.85	$192.90
Purchase #5	$67.28	6.501%	$71.6539	$71.65	$71.65	$71.70
Purchase #6	$83.58	3.281%	$86.3223	$86.32	$86.30	$86.30
Purchase #7	$62.81	5.663%	$66.3669	$66.37	$66.35	$66.40
7 purchase totals =	$710.96		$768.9974	$769.00	$768.95	$769.10