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	$44.82	3.822%	$46.533	$46.53	$46.55	$46.50
Purchase #2	$201.40	6.487%	$214.4648	$214.46	$214.45	$214.50
Purchase #3	$98.91	13.766%	$112.526	$112.53	$112.55	$112.50
Purchase #4	$57.57	8.732%	$62.597	$62.60	$62.60	$62.60
Purchase #5	$66.73	6.183%	$70.8559	$70.86	$70.85	$70.90
Purchase #6	$42.49	12.695%	$47.8841	$47.88	$47.90	$47.90
Purchase #7	$235.56	8.408%	$255.3659	$255.37	$255.35	$255.40
7 purchase totals =	$747.48		$810.2267	$810.23	$810.25	$810.30