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	$224.31	11.704%	$250.5632	$250.56	$250.55	$250.60
Purchase #2	$224.63	13.198%	$254.2767	$254.28	$254.30	$254.30
Purchase #3	$72.85	9.286%	$79.6149	$79.61	$79.60	$79.60
Purchase #4	$195.72	8.509%	$212.3738	$212.37	$212.35	$212.40
Purchase #5	$82.33	12.351%	$92.4986	$92.50	$92.50	$92.50
Purchase #6	$67.40	6.617%	$71.8599	$71.86	$71.85	$71.90
Purchase #7	$144.63	7.143%	$154.9609	$154.96	$154.95	$155.00
7 purchase totals =	$1,011.87		$1,116.1480	$1,116.14	$1,116.10	$1,116.30