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	$162.70	3.208%	$167.9194	$167.92	$167.90	$167.90
Purchase #2	$234.68	8.333%	$254.2359	$254.24	$254.25	$254.20
Purchase #3	$169.36	7.369%	$181.8401	$181.84	$181.85	$181.80
Purchase #4	$60.66	9.589%	$66.4767	$66.48	$66.50	$66.50
Purchase #5	$229.53	11.721%	$256.4332	$256.43	$256.45	$256.40
Purchase #6	$180.65	9.797%	$198.3483	$198.35	$198.35	$198.30
Purchase #7	$78.93	13.554%	$89.6282	$89.63	$89.65	$89.60
7 purchase totals =	$1,116.51		$1,214.8818	$1,214.89	$1,214.95	$1,214.70