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	$65.71	12.590%	$73.9829	$73.98	$74.00	$74.00
Purchase #2	$64.56	3.640%	$66.91	$66.91	$66.90	$66.90
Purchase #3	$140.45	9.524%	$153.8265	$153.83	$153.85	$153.80
Purchase #4	$93.96	13.156%	$106.3214	$106.32	$106.30	$106.30
Purchase #5	$205.94	12.798%	$232.2962	$232.30	$232.30	$232.30
Purchase #6	$72.77	7.328%	$78.1026	$78.10	$78.10	$78.10
Purchase #7	$198.50	11.729%	$221.7821	$221.78	$221.80	$221.80
7 purchase totals =	$841.89		$933.2217	$933.22	$933.25	$933.20