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	$170.50	8.763%	$185.4409	$185.44	$185.45	$185.40
Purchase #2	$40.89	6.798%	$43.6697	$43.67	$43.65	$43.70
Purchase #3	$89.57	6.860%	$95.7145	$95.71	$95.70	$95.70
Purchase #4	$228.63	11.806%	$255.6221	$255.62	$255.60	$255.60
Purchase #5	$230.65	3.404%	$238.5013	$238.50	$238.50	$238.50
Purchase #6	$183.75	12.280%	$206.3145	$206.31	$206.30	$206.30
Purchase #7	$119.40	12.129%	$133.882	$133.88	$133.90	$133.90
7 purchase totals =	$1,063.39		$1,159.1450	$1,159.13	$1,159.10	$1,159.10