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	$139.56	3.729%	$144.7642	$144.76	$144.75	$144.80
Purchase #2	$178.74	4.343%	$186.5027	$186.50	$186.50	$186.50
Purchase #3	$152.60	5.116%	$160.407	$160.41	$160.40	$160.40
Purchase #4	$113.44	11.119%	$126.0534	$126.05	$126.05	$126.10
Purchase #5	$195.83	6.382%	$208.3279	$208.33	$208.35	$208.30
Purchase #6	$57.49	6.591%	$61.2792	$61.28	$61.30	$61.30
Purchase #7	$114.90	12.658%	$129.444	$129.44	$129.45	$129.40
7 purchase totals =	$952.56		$1,016.7784	$1,016.77	$1,016.80	$1,016.80