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	$131.65	9.498%	$144.1541	$144.15	$144.15	$144.20
Purchase #2	$44.47	11.618%	$49.6365	$49.64	$49.65	$49.60
Purchase #3	$156.93	9.596%	$171.989	$171.99	$172.00	$172.00
Purchase #4	$118.29	4.112%	$123.1541	$123.15	$123.15	$123.20
Purchase #5	$42.34	7.514%	$45.5214	$45.52	$45.50	$45.50
Purchase #6	$43.40	8.613%	$47.138	$47.14	$47.15	$47.10
Purchase #7	$97.65	6.250%	$103.7531	$103.75	$103.75	$103.80
7 purchase totals =	$634.73		$685.3462	$685.34	$685.35	$685.40