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	$226.61	8.257%	$245.3212	$245.32	$245.30	$245.30
Purchase #2	$70.37	3.484%	$72.8217	$72.82	$72.80	$72.80
Purchase #3	$72.86	11.757%	$81.4262	$81.43	$81.45	$81.40
Purchase #4	$93.51	4.814%	$98.0116	$98.01	$98.00	$98.00
Purchase #5	$84.39	5.624%	$89.1361	$89.14	$89.15	$89.10
Purchase #6	$103.71	6.282%	$110.2251	$110.23	$110.25	$110.20
Purchase #7	$236.63	4.835%	$248.0711	$248.07	$248.05	$248.10
7 purchase totals =	$888.08		$945.0130	$945.02	$945.00	$944.90