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	$145.72	11.676%	$162.7343	$162.73	$162.75	$162.70
Purchase #2	$97.94	9.151%	$106.9025	$106.90	$106.90	$106.90
Purchase #3	$110.26	8.393%	$119.5141	$119.51	$119.50	$119.50
Purchase #4	$143.45	13.602%	$162.9621	$162.96	$162.95	$163.00
Purchase #5	$128.54	12.260%	$144.299	$144.30	$144.30	$144.30
Purchase #6	$83.82	7.539%	$90.1392	$90.14	$90.15	$90.10
Purchase #7	$39.65	6.411%	$42.192	$42.19	$42.20	$42.20
7 purchase totals =	$749.38		$828.7432	$828.73	$828.75	$828.70