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	$148.69	13.790%	$169.1944	$169.19	$169.20	$169.20
Purchase #2	$41.67	3.386%	$43.0809	$43.08	$43.10	$43.10
Purchase #3	$105.78	12.666%	$119.1781	$119.18	$119.20	$119.20
Purchase #4	$98.64	9.351%	$107.8638	$107.86	$107.85	$107.90
Purchase #5	$158.86	13.202%	$179.8327	$179.83	$179.85	$179.80
Purchase #6	$57.69	3.793%	$59.8782	$59.88	$59.90	$59.90
Purchase #7	$31.29	9.479%	$34.256	$34.26	$34.25	$34.30
7 purchase totals =	$642.62		$713.2841	$713.28	$713.35	$713.40