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	$105.90	9.138%	$115.5771	$115.58	$115.60	$115.60
Purchase #2	$82.68	12.637%	$93.1283	$93.13	$93.15	$93.10
Purchase #3	$106.73	4.739%	$111.7879	$111.79	$111.80	$111.80
Purchase #4	$94.46	6.795%	$100.8786	$100.88	$100.90	$100.90
Purchase #5	$199.92	9.400%	$218.7125	$218.71	$218.70	$218.70
Purchase #6	$120.41	8.792%	$130.9964	$131.00	$131.00	$131.00
Purchase #7	$242.77	11.576%	$270.8731	$270.87	$270.85	$270.90
7 purchase totals =	$952.87		$1,041.9539	$1,041.96	$1,042.00	$1,042.00