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	$171.98	5.564%	$181.549	$181.55	$181.55	$181.50
Purchase #2	$89.88	12.370%	$100.9982	$101.00	$101.00	$101.00
Purchase #3	$236.77	3.547%	$245.1682	$245.17	$245.15	$245.20
Purchase #4	$103.92	4.825%	$108.9341	$108.93	$108.95	$108.90
Purchase #5	$59.85	3.388%	$61.8777	$61.88	$61.90	$61.90
Purchase #6	$171.71	13.188%	$194.3551	$194.36	$194.35	$194.40
Purchase #7	$156.59	10.428%	$172.9192	$172.92	$172.90	$172.90
7 purchase totals =	$990.70		$1,065.8015	$1,065.81	$1,065.80	$1,065.80