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	$81.32	7.491%	$87.4117	$87.41	$87.40	$87.40
Purchase #2	$172.91	7.819%	$186.4298	$186.43	$186.45	$186.40
Purchase #3	$165.25	12.260%	$185.5097	$185.51	$185.50	$185.50
Purchase #4	$141.86	13.607%	$161.1629	$161.16	$161.15	$161.20
Purchase #5	$48.54	13.363%	$55.0264	$55.03	$55.05	$55.00
Purchase #6	$107.70	4.800%	$112.8696	$112.87	$112.85	$112.90
Purchase #7	$158.70	3.815%	$164.7544	$164.75	$164.75	$164.80
7 purchase totals =	$876.28		$953.1645	$953.16	$953.15	$953.20