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	$233.32	9.795%	$256.1737	$256.17	$256.15	$256.20
Purchase #2	$132.31	10.148%	$145.7368	$145.74	$145.75	$145.70
Purchase #3	$77.73	13.191%	$87.9834	$87.98	$88.00	$88.00
Purchase #4	$82.34	9.387%	$90.0693	$90.07	$90.05	$90.10
Purchase #5	$89.49	7.672%	$96.3557	$96.36	$96.35	$96.40
Purchase #6	$197.97	3.720%	$205.3345	$205.33	$205.35	$205.30
Purchase #7	$63.69	12.558%	$71.6882	$71.69	$71.70	$71.70
7 purchase totals =	$876.85		$953.3416	$953.34	$953.35	$953.40