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	$144.42	6.109%	$153.2426	$153.24	$153.25	$153.20
Purchase #2	$30.54	13.316%	$34.6067	$34.61	$34.60	$34.60
Purchase #3	$165.49	4.488%	$172.9172	$172.92	$172.90	$172.90
Purchase #4	$59.43	12.833%	$67.0567	$67.06	$67.05	$67.10
Purchase #5	$191.72	4.383%	$200.1231	$200.12	$200.10	$200.10
Purchase #6	$32.64	7.526%	$35.0965	$35.10	$35.10	$35.10
Purchase #7	$91.99	11.165%	$102.2607	$102.26	$102.25	$102.30
7 purchase totals =	$716.23		$765.3035	$765.31	$765.25	$765.30