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	$174.55	6.765%	$186.3583	$186.36	$186.35	$186.40
Purchase #2	$53.37	4.640%	$55.8464	$55.85	$55.85	$55.80
Purchase #3	$88.83	8.757%	$96.6088	$96.61	$96.60	$96.60
Purchase #4	$55.92	10.665%	$61.8839	$61.88	$61.90	$61.90
Purchase #5	$176.85	8.678%	$192.197	$192.20	$192.20	$192.20
Purchase #6	$206.93	5.773%	$218.8761	$218.88	$218.90	$218.90
Purchase #7	$106.39	4.482%	$111.1584	$111.16	$111.15	$111.20
7 purchase totals =	$862.84		$922.9289	$922.94	$922.95	$923.00