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	$186.69	10.468%	$206.2327	$206.23	$206.25	$206.20
Purchase #2	$92.85	13.734%	$105.602	$105.60	$105.60	$105.60
Purchase #3	$118.70	4.392%	$123.9133	$123.91	$123.90	$123.90
Purchase #4	$207.45	11.535%	$231.3794	$231.38	$231.40	$231.40
Purchase #5	$54.55	13.869%	$62.1155	$62.12	$62.10	$62.10
Purchase #6	$237.95	5.665%	$251.4299	$251.43	$251.45	$251.40
Purchase #7	$131.53	8.475%	$142.6772	$142.68	$142.70	$142.70
7 purchase totals =	$1,029.72		$1,123.3500	$1,123.35	$1,123.40	$1,123.30