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	$110.59	11.225%	$123.0037	$123.00	$123.00	$123.00
Purchase #2	$197.87	11.136%	$219.9048	$219.90	$219.90	$219.90
Purchase #3	$134.91	3.205%	$139.2339	$139.23	$139.25	$139.20
Purchase #4	$161.60	3.240%	$166.8358	$166.84	$166.85	$166.80
Purchase #5	$185.28	8.252%	$200.5693	$200.57	$200.55	$200.60
Purchase #6	$89.99	6.614%	$95.9419	$95.94	$95.95	$95.90
Purchase #7	$106.37	7.478%	$114.3243	$114.32	$114.30	$114.30
7 purchase totals =	$986.61		$1,059.8137	$1,059.80	$1,059.80	$1,059.70