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	$245.75	6.520%	$261.7729	$261.77	$261.75	$261.80
Purchase #2	$84.55	12.518%	$95.134	$95.13	$95.15	$95.10
Purchase #3	$136.34	4.667%	$142.703	$142.70	$142.70	$142.70
Purchase #4	$90.46	9.510%	$99.0627	$99.06	$99.05	$99.10
Purchase #5	$134.50	3.442%	$139.1295	$139.13	$139.15	$139.10
Purchase #6	$40.63	5.528%	$42.876	$42.88	$42.90	$42.90
Purchase #7	$138.95	8.247%	$150.4092	$150.41	$150.40	$150.40
7 purchase totals =	$871.18		$931.0873	$931.08	$931.10	$931.10