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	$179.90	3.331%	$185.8925	$185.89	$185.90	$185.90
Purchase #2	$12.38	9.114%	$13.5083	$13.51	$13.50	$13.50
Purchase #3	$40.47	8.542%	$43.9269	$43.93	$43.95	$43.90
Purchase #4	$41.39	7.435%	$44.4673	$44.47	$44.45	$44.50
Purchase #5	$49.51	9.663%	$54.2942	$54.29	$54.30	$54.30
Purchase #6	$173.99	10.513%	$192.2816	$192.28	$192.30	$192.30
Purchase #7	$119.62	3.765%	$124.1237	$124.12	$124.10	$124.10
7 purchase totals =	$617.26		$658.4945	$658.49	$658.50	$658.50