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	$43.67	7.674%	$47.0212	$47.02	$47.00	$47.00
Purchase #2	$27.73	13.144%	$31.3748	$31.37	$31.35	$31.40
Purchase #3	$33.88	11.821%	$37.885	$37.89	$37.90	$37.90
Purchase #4	$179.82	7.182%	$192.7347	$192.73	$192.75	$192.70
Purchase #5	$37.97	7.245%	$40.7209	$40.72	$40.70	$40.70
Purchase #6	$115.29	12.782%	$130.0264	$130.03	$130.05	$130.00
Purchase #7	$73.58	11.555%	$82.0822	$82.08	$82.10	$82.10
7 purchase totals =	$511.94		$561.8452	$561.84	$561.85	$561.80