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	$178.46	9.366%	$195.1746	$195.17	$195.15	$195.20
Purchase #2	$206.60	4.341%	$215.5685	$215.57	$215.55	$215.60
Purchase #3	$64.80	4.694%	$67.8417	$67.84	$67.85	$67.80
Purchase #4	$172.39	12.365%	$193.706	$193.71	$193.70	$193.70
Purchase #5	$204.60	8.628%	$222.2529	$222.25	$222.25	$222.30
Purchase #6	$62.82	6.867%	$67.1338	$67.13	$67.15	$67.10
Purchase #7	$96.78	12.725%	$109.0953	$109.10	$109.10	$109.10
7 purchase totals =	$986.45		$1,070.7728	$1,070.77	$1,070.75	$1,070.80