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	$114.92	7.823%	$123.9102	$123.91	$123.90	$123.90
Purchase #2	$52.99	6.117%	$56.2314	$56.23	$56.25	$56.20
Purchase #3	$237.69	3.463%	$245.9212	$245.92	$245.90	$245.90
Purchase #4	$203.46	5.138%	$213.9138	$213.91	$213.90	$213.90
Purchase #5	$172.49	5.870%	$182.6152	$182.62	$182.60	$182.60
Purchase #6	$87.67	12.332%	$98.4815	$98.48	$98.50	$98.50
Purchase #7	$96.63	7.721%	$104.0908	$104.09	$104.10	$104.10
7 purchase totals =	$965.85		$1,025.1641	$1,025.16	$1,025.15	$1,025.10