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	$224.31	5.815%	$237.3536	$237.35	$237.35	$237.40
Purchase #2	$82.32	10.136%	$90.664	$90.66	$90.65	$90.70
Purchase #3	$153.67	11.421%	$171.2207	$171.22	$171.20	$171.20
Purchase #4	$190.89	6.743%	$203.7617	$203.76	$203.75	$203.80
Purchase #5	$214.34	12.173%	$240.4316	$240.43	$240.45	$240.40
Purchase #6	$237.30	3.421%	$245.418	$245.42	$245.40	$245.40
Purchase #7	$46.89	5.625%	$49.5276	$49.53	$49.55	$49.50
7 purchase totals =	$1,149.72		$1,238.3772	$1,238.37	$1,238.35	$1,238.40