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	$173.79	6.754%	$185.5278	$185.53	$185.55	$185.50
Purchase #2	$37.85	6.676%	$40.3769	$40.38	$40.40	$40.40
Purchase #3	$215.97	5.761%	$228.412	$228.41	$228.40	$228.40
Purchase #4	$73.89	8.466%	$80.1455	$80.15	$80.15	$80.10
Purchase #5	$55.60	11.465%	$61.9745	$61.97	$61.95	$62.00
Purchase #6	$30.64	3.329%	$31.66	$31.66	$31.65	$31.70
Purchase #7	$228.46	13.638%	$259.6174	$259.62	$259.60	$259.60
7 purchase totals =	$816.20		$887.7141	$887.72	$887.70	$887.70