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	$111.72	10.163%	$123.0741	$123.07	$123.05	$123.10
Purchase #2	$75.54	9.795%	$82.9391	$82.94	$82.95	$82.90
Purchase #3	$204.52	11.638%	$228.322	$228.32	$228.30	$228.30
Purchase #4	$93.84	12.575%	$105.6404	$105.64	$105.65	$105.60
Purchase #5	$104.33	10.469%	$115.2523	$115.25	$115.25	$115.30
Purchase #6	$24.43	13.820%	$27.8062	$27.81	$27.80	$27.80
Purchase #7	$41.39	4.362%	$43.1954	$43.20	$43.20	$43.20
7 purchase totals =	$655.77		$726.2295	$726.23	$726.20	$726.20