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	$144.49	5.398%	$152.2896	$152.29	$152.30	$152.30
Purchase #2	$114.38	8.292%	$123.8644	$123.86	$123.85	$123.90
Purchase #3	$98.58	11.719%	$110.1326	$110.13	$110.15	$110.10
Purchase #4	$50.80	12.814%	$57.3095	$57.31	$57.30	$57.30
Purchase #5	$141.50	12.614%	$159.3488	$159.35	$159.35	$159.30
Purchase #6	$36.72	5.271%	$38.6555	$38.66	$38.65	$38.70
Purchase #7	$116.77	6.728%	$124.6263	$124.63	$124.65	$124.60
7 purchase totals =	$703.24		$766.2267	$766.23	$766.25	$766.20