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	$166.82	11.155%	$185.4288	$185.43	$185.45	$185.40
Purchase #2	$94.74	8.628%	$102.9142	$102.91	$102.90	$102.90
Purchase #3	$52.64	12.539%	$59.2405	$59.24	$59.25	$59.20
Purchase #4	$86.84	3.715%	$90.0661	$90.07	$90.05	$90.10
Purchase #5	$196.59	9.267%	$214.808	$214.81	$214.80	$214.80
Purchase #6	$196.58	9.632%	$215.5146	$215.51	$215.50	$215.50
Purchase #7	$115.45	3.414%	$119.3915	$119.39	$119.40	$119.40
7 purchase totals =	$909.66		$987.3637	$987.36	$987.35	$987.30