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	$125.73	13.699%	$142.9538	$142.95	$142.95	$143.00
Purchase #2	$81.91	9.195%	$89.4416	$89.44	$89.45	$89.40
Purchase #3	$27.71	12.850%	$31.2707	$31.27	$31.25	$31.30
Purchase #4	$50.89	10.464%	$56.2151	$56.22	$56.20	$56.20
Purchase #5	$147.94	3.854%	$153.6416	$153.64	$153.65	$153.60
Purchase #6	$43.55	6.397%	$46.3359	$46.34	$46.35	$46.30
Purchase #7	$242.88	9.568%	$266.1188	$266.12	$266.10	$266.10
7 purchase totals =	$720.61		$785.9775	$785.98	$785.95	$785.90