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	$197.33	7.110%	$211.3602	$211.36	$211.35	$211.40
Purchase #2	$231.81	5.788%	$245.2272	$245.23	$245.25	$245.20
Purchase #3	$208.37	6.371%	$221.6453	$221.65	$221.65	$221.60
Purchase #4	$173.88	13.151%	$196.747	$196.75	$196.75	$196.70
Purchase #5	$170.56	4.848%	$178.8287	$178.83	$178.85	$178.80
Purchase #6	$231.94	7.420%	$249.1499	$249.15	$249.15	$249.10
Purchase #7	$40.51	12.475%	$45.5636	$45.56	$45.55	$45.60
7 purchase totals =	$1,254.40		$1,348.5219	$1,348.53	$1,348.55	$1,348.40