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	$94.56	10.808%	$104.78	$104.78	$104.80	$104.80
Purchase #2	$61.88	9.396%	$67.6942	$67.69	$67.70	$67.70
Purchase #3	$33.98	10.506%	$37.5499	$37.55	$37.55	$37.50
Purchase #4	$80.46	12.405%	$90.4411	$90.44	$90.45	$90.40
Purchase #5	$50.59	12.738%	$57.0342	$57.03	$57.05	$57.00
Purchase #6	$56.47	13.644%	$64.1748	$64.17	$64.15	$64.20
Purchase #7	$208.29	9.839%	$228.7837	$228.78	$228.80	$228.80
7 purchase totals =	$586.23		$650.4579	$650.44	$650.50	$650.40