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	$126.62	11.639%	$141.3573	$141.36	$141.35	$141.40
Purchase #2	$180.92	8.461%	$196.2276	$196.23	$196.25	$196.20
Purchase #3	$29.73	11.597%	$33.1778	$33.18	$33.20	$33.20
Purchase #4	$249.82	6.795%	$266.7953	$266.80	$266.80	$266.80
Purchase #5	$34.97	5.630%	$36.9388	$36.94	$36.95	$36.90
Purchase #6	$112.31	7.581%	$120.8242	$120.82	$120.80	$120.80
Purchase #7	$212.46	4.151%	$221.2792	$221.28	$221.30	$221.30
7 purchase totals =	$946.83		$1,016.6002	$1,016.61	$1,016.65	$1,016.60