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	$151.88	4.833%	$159.2204	$159.22	$159.20	$159.20
Purchase #2	$160.40	3.482%	$165.9851	$165.99	$166.00	$166.00
Purchase #3	$7.78	5.836%	$8.234	$8.23	$8.25	$8.20
Purchase #4	$67.55	6.605%	$72.0117	$72.01	$72.00	$72.00
Purchase #5	$118.36	4.527%	$123.7182	$123.72	$123.70	$123.70
Purchase #6	$137.54	9.225%	$150.2281	$150.23	$150.25	$150.20
Purchase #7	$163.39	13.560%	$185.5457	$185.55	$185.55	$185.50
7 purchase totals =	$806.90		$864.9432	$864.95	$864.95	$864.80