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	$90.35	8.850%	$98.346	$98.35	$98.35	$98.30
Purchase #2	$154.94	6.847%	$165.5487	$165.55	$165.55	$165.50
Purchase #3	$101.79	10.293%	$112.2672	$112.27	$112.25	$112.30
Purchase #4	$48.31	10.507%	$53.3859	$53.39	$53.40	$53.40
Purchase #5	$144.41	11.473%	$160.9782	$160.98	$161.00	$161.00
Purchase #6	$51.96	5.530%	$54.8334	$54.83	$54.85	$54.80
Purchase #7	$195.43	13.511%	$221.8345	$221.83	$221.85	$221.80
7 purchase totals =	$787.19		$867.1939	$867.20	$867.25	$867.10