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	$198.88	10.310%	$219.3845	$219.38	$219.40	$219.40
Purchase #2	$134.25	4.205%	$139.8952	$139.90	$139.90	$139.90
Purchase #3	$184.56	8.786%	$200.7754	$200.78	$200.80	$200.80
Purchase #4	$28.95	5.655%	$30.5871	$30.59	$30.60	$30.60
Purchase #5	$207.70	7.795%	$223.8902	$223.89	$223.90	$223.90
Purchase #6	$242.37	13.836%	$275.9043	$275.90	$275.90	$275.90
Purchase #7	$20.83	13.525%	$23.6473	$23.65	$23.65	$23.60
7 purchase totals =	$1,017.54		$1,114.0840	$1,114.09	$1,114.15	$1,114.10