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	$160.92	8.162%	$174.0543	$174.05	$174.05	$174.10
Purchase #2	$69.68	13.223%	$78.8938	$78.89	$78.90	$78.90
Purchase #3	$170.89	13.746%	$194.3805	$194.38	$194.40	$194.40
Purchase #4	$76.73	11.566%	$85.6046	$85.60	$85.60	$85.60
Purchase #5	$160.34	12.362%	$180.1612	$180.16	$180.15	$180.20
Purchase #6	$158.86	4.587%	$166.1469	$166.15	$166.15	$166.10
Purchase #7	$222.52	9.310%	$243.2366	$243.24	$243.25	$243.20
7 purchase totals =	$1,019.94		$1,122.4779	$1,122.47	$1,122.50	$1,122.50