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	$99.96	13.872%	$113.8265	$113.83	$113.85	$113.80
Purchase #2	$56.74	8.626%	$61.6344	$61.63	$61.65	$61.60
Purchase #3	$199.41	11.328%	$221.9992	$222.00	$222.00	$222.00
Purchase #4	$93.97	5.681%	$99.3084	$99.31	$99.30	$99.30
Purchase #5	$183.77	9.272%	$200.8092	$200.81	$200.80	$200.80
Purchase #6	$72.52	7.566%	$78.0069	$78.01	$78.00	$78.00
Purchase #7	$223.86	8.746%	$243.4388	$243.44	$243.45	$243.40
7 purchase totals =	$930.23		$1,019.0234	$1,019.03	$1,019.05	$1,018.90