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	$210.65	3.319%	$217.6415	$217.64	$217.65	$217.60
Purchase #2	$39.77	7.546%	$42.771	$42.77	$42.75	$42.80
Purchase #3	$62.83	7.151%	$67.323	$67.32	$67.30	$67.30
Purchase #4	$30.84	6.279%	$32.7764	$32.78	$32.80	$32.80
Purchase #5	$126.62	10.830%	$140.3329	$140.33	$140.35	$140.30
Purchase #6	$175.32	11.552%	$195.573	$195.57	$195.55	$195.60
Purchase #7	$12.41	5.828%	$13.1333	$13.13	$13.15	$13.10
7 purchase totals =	$658.44		$709.5511	$709.54	$709.55	$709.50