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	$151.29	8.545%	$164.2177	$164.22	$164.20	$164.20
Purchase #2	$235.49	10.369%	$259.908	$259.91	$259.90	$259.90
Purchase #3	$30.61	5.619%	$32.33	$32.33	$32.35	$32.30
Purchase #4	$54.78	3.260%	$56.5658	$56.57	$56.55	$56.60
Purchase #5	$80.40	13.572%	$91.3119	$91.31	$91.30	$91.30
Purchase #6	$201.55	9.310%	$220.3143	$220.31	$220.30	$220.30
Purchase #7	$215.44	12.147%	$241.6095	$241.61	$241.60	$241.60
7 purchase totals =	$969.56		$1,066.2572	$1,066.26	$1,066.20	$1,066.20