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	$105.71	5.544%	$111.5706	$111.57	$111.55	$111.60
Purchase #2	$55.39	6.718%	$59.1111	$59.11	$59.10	$59.10
Purchase #3	$93.78	5.108%	$98.5703	$98.57	$98.55	$98.60
Purchase #4	$104.46	4.819%	$109.4939	$109.49	$109.50	$109.50
Purchase #5	$221.95	7.697%	$239.0335	$239.03	$239.05	$239.00
Purchase #6	$137.99	13.309%	$156.3551	$156.36	$156.35	$156.40
Purchase #7	$146.30	9.700%	$160.4911	$160.49	$160.50	$160.50
7 purchase totals =	$865.58		$934.6256	$934.62	$934.60	$934.70