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	$141.37	5.290%	$148.8485	$148.85	$148.85	$148.80
Purchase #2	$127.96	10.128%	$140.9198	$140.92	$140.90	$140.90
Purchase #3	$56.83	8.662%	$61.7526	$61.75	$61.75	$61.80
Purchase #4	$231.40	10.579%	$255.8798	$255.88	$255.90	$255.90
Purchase #5	$244.67	6.230%	$259.9129	$259.91	$259.90	$259.90
Purchase #6	$95.31	6.664%	$101.6615	$101.66	$101.65	$101.70
Purchase #7	$47.25	10.803%	$52.3544	$52.35	$52.35	$52.40
7 purchase totals =	$944.79		$1,021.3295	$1,021.32	$1,021.30	$1,021.40