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	$156.76	7.558%	$168.6079	$168.61	$168.60	$168.60
Purchase #2	$36.63	11.715%	$40.9212	$40.92	$40.90	$40.90
Purchase #3	$142.41	5.401%	$150.1016	$150.10	$150.10	$150.10
Purchase #4	$128.45	5.866%	$135.9849	$135.98	$136.00	$136.00
Purchase #5	$61.82	8.841%	$67.2855	$67.29	$67.30	$67.30
Purchase #6	$133.37	8.833%	$145.1506	$145.15	$145.15	$145.20
Purchase #7	$156.34	3.446%	$161.7275	$161.73	$161.75	$161.70
7 purchase totals =	$815.78		$869.7792	$869.78	$869.80	$869.80