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	$218.90	3.458%	$226.4696	$226.47	$226.45	$226.50
Purchase #2	$62.36	4.595%	$65.2254	$65.23	$65.25	$65.20
Purchase #3	$38.76	6.144%	$41.1414	$41.14	$41.15	$41.10
Purchase #4	$19.82	7.750%	$21.3561	$21.36	$21.35	$21.40
Purchase #5	$17.80	8.627%	$19.3356	$19.34	$19.35	$19.30
Purchase #6	$85.28	4.861%	$89.4255	$89.43	$89.45	$89.40
Purchase #7	$80.87	11.769%	$90.3876	$90.39	$90.40	$90.40
7 purchase totals =	$523.79		$553.3412	$553.36	$553.40	$553.30