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	$163.34	11.250%	$181.7158	$181.72	$181.70	$181.70
Purchase #2	$25.59	5.670%	$27.041	$27.04	$27.05	$27.00
Purchase #3	$193.83	13.814%	$220.6057	$220.61	$220.60	$220.60
Purchase #4	$17.34	7.245%	$18.5963	$18.60	$18.60	$18.60
Purchase #5	$89.73	8.728%	$97.5616	$97.56	$97.55	$97.60
Purchase #6	$75.82	9.328%	$82.8925	$82.89	$82.90	$82.90
Purchase #7	$132.74	13.493%	$150.6506	$150.65	$150.65	$150.70
7 purchase totals =	$698.39		$779.0635	$779.07	$779.05	$779.10