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	$65.44	9.809%	$71.859	$71.86	$71.85	$71.90
Purchase #2	$185.70	5.476%	$195.8689	$195.87	$195.85	$195.90
Purchase #3	$184.73	8.764%	$200.9197	$200.92	$200.90	$200.90
Purchase #4	$168.45	11.342%	$187.5556	$187.56	$187.55	$187.60
Purchase #5	$171.40	12.403%	$192.6587	$192.66	$192.65	$192.70
Purchase #6	$119.74	9.824%	$131.5033	$131.50	$131.50	$131.50
Purchase #7	$137.92	3.752%	$143.0948	$143.09	$143.10	$143.10
7 purchase totals =	$1,033.38		$1,123.4600	$1,123.46	$1,123.40	$1,123.60