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	$160.71	4.482%	$167.913	$167.91	$167.90	$167.90
Purchase #2	$126.91	12.648%	$142.9616	$142.96	$142.95	$143.00
Purchase #3	$205.32	4.335%	$214.2206	$214.22	$214.20	$214.20
Purchase #4	$39.75	6.111%	$42.1791	$42.18	$42.20	$42.20
Purchase #5	$72.38	3.421%	$74.8561	$74.86	$74.85	$74.90
Purchase #6	$61.57	6.600%	$65.6336	$65.63	$65.65	$65.60
Purchase #7	$123.78	3.864%	$128.5629	$128.56	$128.55	$128.60
7 purchase totals =	$790.42		$836.3269	$836.32	$836.30	$836.40