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	$46.37	9.730%	$50.8818	$50.88	$50.90	$50.90
Purchase #2	$214.57	4.176%	$223.5304	$223.53	$223.55	$223.50
Purchase #3	$63.43	5.356%	$66.8273	$66.83	$66.85	$66.80
Purchase #4	$192.95	10.805%	$213.7982	$213.80	$213.80	$213.80
Purchase #5	$170.78	8.852%	$185.8974	$185.90	$185.90	$185.90
Purchase #6	$163.49	13.109%	$184.9219	$184.92	$184.90	$184.90
Purchase #7	$91.25	6.459%	$97.1438	$97.14	$97.15	$97.10
7 purchase totals =	$942.84		$1,023.0008	$1,023.00	$1,023.05	$1,022.90