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	$117.78	10.675%	$130.353	$130.35	$130.35	$130.40
Purchase #2	$170.61	11.686%	$190.5475	$190.55	$190.55	$190.50
Purchase #3	$181.28	12.843%	$204.5618	$204.56	$204.55	$204.60
Purchase #4	$104.60	7.314%	$112.2504	$112.25	$112.25	$112.30
Purchase #5	$40.95	5.394%	$43.1588	$43.16	$43.15	$43.20
Purchase #6	$117.41	7.304%	$125.9856	$125.99	$126.00	$126.00
Purchase #7	$155.30	8.516%	$168.5253	$168.53	$168.55	$168.50
7 purchase totals =	$887.93		$975.3824	$975.39	$975.40	$975.50