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	$138.89	11.479%	$154.8332	$154.83	$154.85	$154.80
Purchase #2	$162.54	9.136%	$177.3897	$177.39	$177.40	$177.40
Purchase #3	$113.51	12.644%	$127.8622	$127.86	$127.85	$127.90
Purchase #4	$95.30	4.705%	$99.7839	$99.78	$99.80	$99.80
Purchase #5	$211.32	8.517%	$229.3181	$229.32	$229.30	$229.30
Purchase #6	$37.60	11.584%	$41.9556	$41.96	$41.95	$42.00
Purchase #7	$137.25	13.374%	$155.6058	$155.61	$155.60	$155.60
7 purchase totals =	$896.41		$986.7485	$986.75	$986.75	$986.80