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	$207.34	5.614%	$218.9801	$218.98	$219.00	$219.00
Purchase #2	$40.85	5.564%	$43.1229	$43.12	$43.10	$43.10
Purchase #3	$198.57	13.810%	$225.9925	$225.99	$226.00	$226.00
Purchase #4	$76.92	4.441%	$80.336	$80.34	$80.35	$80.30
Purchase #5	$12.76	8.385%	$13.8299	$13.83	$13.85	$13.80
Purchase #6	$82.98	9.465%	$90.8341	$90.83	$90.85	$90.80
Purchase #7	$150.91	6.176%	$160.2302	$160.23	$160.25	$160.20
7 purchase totals =	$770.33		$833.3257	$833.32	$833.40	$833.20