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	$150.65	11.599%	$168.1239	$168.12	$168.10	$168.10
Purchase #2	$20.74	5.119%	$21.8017	$21.80	$21.80	$21.80
Purchase #3	$120.37	13.288%	$136.3648	$136.36	$136.35	$136.40
Purchase #4	$80.29	7.816%	$86.5655	$86.57	$86.55	$86.60
Purchase #5	$10.82	13.663%	$12.2983	$12.30	$12.30	$12.30
Purchase #6	$177.35	8.336%	$192.1339	$192.13	$192.15	$192.10
Purchase #7	$89.91	11.442%	$100.1975	$100.20	$100.20	$100.20
7 purchase totals =	$650.13		$717.4856	$717.48	$717.45	$717.50