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	$156.69	9.694%	$171.8795	$171.88	$171.90	$171.90
Purchase #2	$187.98	4.211%	$195.8958	$195.90	$195.90	$195.90
Purchase #3	$82.84	9.450%	$90.6684	$90.67	$90.65	$90.70
Purchase #4	$242.95	13.470%	$275.6754	$275.68	$275.70	$275.70
Purchase #5	$179.46	9.302%	$196.1534	$196.15	$196.15	$196.20
Purchase #6	$155.50	8.296%	$168.4003	$168.40	$168.40	$168.40
Purchase #7	$118.99	3.717%	$123.4129	$123.41	$123.40	$123.40
7 purchase totals =	$1,124.41		$1,222.0857	$1,222.09	$1,222.10	$1,222.20