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	$223.36	11.414%	$248.8543	$248.85	$248.85	$248.90
Purchase #2	$198.71	6.635%	$211.8944	$211.89	$211.90	$211.90
Purchase #3	$196.62	7.746%	$211.8502	$211.85	$211.85	$211.90
Purchase #4	$54.57	6.274%	$57.9937	$57.99	$58.00	$58.00
Purchase #5	$120.62	13.495%	$136.8977	$136.90	$136.90	$136.90
Purchase #6	$105.63	11.636%	$117.9211	$117.92	$117.90	$117.90
Purchase #7	$173.42	13.513%	$196.8542	$196.85	$196.85	$196.90
7 purchase totals =	$1,072.93		$1,182.2656	$1,182.25	$1,182.25	$1,182.40