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	$38.91	9.134%	$42.464	$42.46	$42.45	$42.50
Purchase #2	$119.64	6.168%	$127.0194	$127.02	$127.00	$127.00
Purchase #3	$17.84	5.243%	$18.7754	$18.78	$18.80	$18.80
Purchase #4	$215.76	7.554%	$232.0585	$232.06	$232.05	$232.10
Purchase #5	$6.74	9.438%	$7.3761	$7.38	$7.40	$7.40
Purchase #6	$80.47	9.242%	$87.907	$87.91	$87.90	$87.90
Purchase #7	$220.94	11.578%	$246.5204	$246.52	$246.50	$246.50
7 purchase totals =	$700.30		$762.1208	$762.13	$762.10	$762.20