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	$213.74	9.727%	$234.5305	$234.53	$234.55	$234.50
Purchase #2	$151.85	8.393%	$164.5948	$164.59	$164.60	$164.60
Purchase #3	$61.31	6.392%	$65.2289	$65.23	$65.25	$65.20
Purchase #4	$119.86	9.832%	$131.6446	$131.64	$131.65	$131.60
Purchase #5	$146.78	3.311%	$151.6399	$151.64	$151.65	$151.60
Purchase #6	$129.26	5.132%	$135.8936	$135.89	$135.90	$135.90
Purchase #7	$213.70	4.539%	$223.3998	$223.40	$223.40	$223.40
7 purchase totals =	$1,036.50		$1,106.9321	$1,106.92	$1,107.00	$1,106.80