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	$242.56	9.356%	$265.2539	$265.25	$265.25	$265.30
Purchase #2	$86.89	12.596%	$97.8347	$97.83	$97.85	$97.80
Purchase #3	$140.54	5.754%	$148.6267	$148.63	$148.65	$148.60
Purchase #4	$38.67	11.530%	$43.1287	$43.13	$43.15	$43.10
Purchase #5	$114.94	10.305%	$126.7846	$126.78	$126.80	$126.80
Purchase #6	$234.84	3.386%	$242.7917	$242.79	$242.80	$242.80
Purchase #7	$89.34	11.244%	$99.3854	$99.39	$99.40	$99.40
7 purchase totals =	$947.78		$1,023.8057	$1,023.80	$1,023.90	$1,023.80