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	$223.54	5.626%	$236.1164	$236.12	$236.10	$236.10
Purchase #2	$240.83	6.592%	$256.7055	$256.71	$256.70	$256.70
Purchase #3	$76.28	3.423%	$78.8911	$78.89	$78.90	$78.90
Purchase #4	$174.88	10.692%	$193.5782	$193.58	$193.60	$193.60
Purchase #5	$7.86	13.686%	$8.9357	$8.94	$8.95	$8.90
Purchase #6	$99.32	8.849%	$108.1088	$108.11	$108.10	$108.10
Purchase #7	$207.82	3.731%	$215.5738	$215.57	$215.55	$215.60
7 purchase totals =	$1,030.53		$1,097.9095	$1,097.92	$1,097.90	$1,097.90