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	$117.56	13.705%	$133.6716	$133.67	$133.65	$133.70
Purchase #2	$177.73	3.767%	$184.4251	$184.43	$184.45	$184.40
Purchase #3	$242.64	5.606%	$256.2424	$256.24	$256.25	$256.20
Purchase #4	$230.72	5.606%	$243.6542	$243.65	$243.65	$243.70
Purchase #5	$17.59	3.770%	$18.2531	$18.25	$18.25	$18.30
Purchase #6	$91.61	8.523%	$99.4179	$99.42	$99.40	$99.40
Purchase #7	$58.56	11.292%	$65.1726	$65.17	$65.15	$65.20
7 purchase totals =	$936.41		$1,000.8369	$1,000.83	$1,000.80	$1,000.90