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	$214.59	3.493%	$222.0856	$222.09	$222.10	$222.10
Purchase #2	$30.64	5.516%	$32.3301	$32.33	$32.35	$32.30
Purchase #3	$192.54	11.255%	$214.2104	$214.21	$214.20	$214.20
Purchase #4	$172.87	5.658%	$182.651	$182.65	$182.65	$182.70
Purchase #5	$85.78	6.520%	$91.3729	$91.37	$91.35	$91.40
Purchase #6	$102.72	11.360%	$114.389	$114.39	$114.40	$114.40
Purchase #7	$201.78	13.595%	$229.212	$229.21	$229.20	$229.20
7 purchase totals =	$1,000.92		$1,086.2510	$1,086.25	$1,086.25	$1,086.30