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	$127.53	10.753%	$141.2433	$141.24	$141.25	$141.20
Purchase #2	$212.88	5.131%	$223.8029	$223.80	$223.80	$223.80
Purchase #3	$121.53	4.779%	$127.3379	$127.34	$127.35	$127.30
Purchase #4	$104.67	6.860%	$111.8504	$111.85	$111.85	$111.90
Purchase #5	$62.80	6.765%	$67.0484	$67.05	$67.05	$67.00
Purchase #6	$29.64	13.815%	$33.7348	$33.73	$33.75	$33.70
Purchase #7	$143.75	8.617%	$156.1369	$156.14	$156.15	$156.10
7 purchase totals =	$802.80		$861.1546	$861.15	$861.20	$861.00