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	$56.28	12.127%	$63.1051	$63.11	$63.10	$63.10
Purchase #2	$9.69	9.520%	$10.6125	$10.61	$10.60	$10.60
Purchase #3	$90.41	11.404%	$100.7204	$100.72	$100.70	$100.70
Purchase #4	$162.36	4.758%	$170.0851	$170.09	$170.10	$170.10
Purchase #5	$90.55	3.295%	$93.5336	$93.53	$93.55	$93.50
Purchase #6	$193.35	10.109%	$212.8958	$212.90	$212.90	$212.90
Purchase #7	$36.33	4.450%	$37.9467	$37.95	$37.95	$37.90
7 purchase totals =	$638.97		$688.8992	$688.91	$688.90	$688.80