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	$243.50	4.533%	$254.5379	$254.54	$254.55	$254.50
Purchase #2	$103.82	9.195%	$113.3662	$113.37	$113.35	$113.40
Purchase #3	$139.82	8.603%	$151.8487	$151.85	$151.85	$151.80
Purchase #4	$219.53	10.339%	$242.2272	$242.23	$242.25	$242.20
Purchase #5	$25.88	7.526%	$27.8277	$27.83	$27.85	$27.80
Purchase #6	$134.25	10.478%	$148.3167	$148.32	$148.30	$148.30
Purchase #7	$171.81	4.696%	$179.8782	$179.88	$179.90	$179.90
7 purchase totals =	$1,038.61		$1,118.0026	$1,118.02	$1,118.05	$1,117.90