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	$87.69	6.777%	$93.6328	$93.63	$93.65	$93.60
Purchase #2	$158.52	3.742%	$164.4518	$164.45	$164.45	$164.50
Purchase #3	$138.89	6.212%	$147.5178	$147.52	$147.50	$147.50
Purchase #4	$127.85	3.113%	$131.83	$131.83	$131.85	$131.80
Purchase #5	$218.88	8.104%	$236.618	$236.62	$236.60	$236.60
Purchase #6	$37.69	9.834%	$41.3964	$41.40	$41.40	$41.40
Purchase #7	$56.72	10.419%	$62.6297	$62.63	$62.65	$62.60
7 purchase totals =	$826.24		$878.0765	$878.08	$878.10	$878.00