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	$103.54	11.449%	$115.3943	$115.39	$115.40	$115.40
Purchase #2	$100.94	9.609%	$110.6393	$110.64	$110.65	$110.60
Purchase #3	$122.76	7.370%	$131.8074	$131.81	$131.80	$131.80
Purchase #4	$53.78	4.672%	$56.2926	$56.29	$56.30	$56.30
Purchase #5	$161.38	7.808%	$173.9806	$173.98	$174.00	$174.00
Purchase #6	$7.53	4.800%	$7.8914	$7.89	$7.90	$7.90
Purchase #7	$117.74	4.663%	$123.2302	$123.23	$123.25	$123.20
7 purchase totals =	$667.67		$719.2358	$719.23	$719.30	$719.20