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	$106.98	10.586%	$118.3049	$118.30	$118.30	$118.30
Purchase #2	$7.58	3.832%	$7.8705	$7.87	$7.85	$7.90
Purchase #3	$160.34	7.806%	$172.8561	$172.86	$172.85	$172.90
Purchase #4	$89.41	5.573%	$94.3928	$94.39	$94.40	$94.40
Purchase #5	$27.92	13.461%	$31.6783	$31.68	$31.70	$31.70
Purchase #6	$228.76	3.542%	$236.8627	$236.86	$236.85	$236.90
Purchase #7	$20.74	5.683%	$21.9187	$21.92	$21.90	$21.90
7 purchase totals =	$641.73		$683.8840	$683.88	$683.85	$684.00