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	$154.98	10.448%	$171.1723	$171.17	$171.15	$171.20
Purchase #2	$163.34	5.547%	$172.4005	$172.40	$172.40	$172.40
Purchase #3	$60.44	7.658%	$65.0685	$65.07	$65.05	$65.10
Purchase #4	$137.49	3.634%	$142.4864	$142.49	$142.50	$142.50
Purchase #5	$97.35	3.192%	$100.4574	$100.46	$100.45	$100.50
Purchase #6	$152.36	12.716%	$171.7341	$171.73	$171.75	$171.70
Purchase #7	$120.37	3.432%	$124.5011	$124.50	$124.50	$124.50
7 purchase totals =	$886.33		$947.8203	$947.82	$947.80	$947.90