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	$38.36	5.180%	$40.347	$40.35	$40.35	$40.30
Purchase #2	$137.86	4.869%	$144.5724	$144.57	$144.55	$144.60
Purchase #3	$36.63	12.539%	$41.223	$41.22	$41.20	$41.20
Purchase #4	$60.97	10.535%	$67.3932	$67.39	$67.40	$67.40
Purchase #5	$125.70	13.417%	$142.5652	$142.57	$142.55	$142.60
Purchase #6	$100.71	5.677%	$106.4273	$106.43	$106.45	$106.40
Purchase #7	$155.73	5.419%	$164.169	$164.17	$164.15	$164.20
7 purchase totals =	$655.96		$706.6971	$706.70	$706.65	$706.70