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	$151.62	3.406%	$156.7842	$156.78	$156.80	$156.80
Purchase #2	$182.77	12.333%	$205.311	$205.31	$205.30	$205.30
Purchase #3	$123.32	8.326%	$133.5876	$133.59	$133.60	$133.60
Purchase #4	$177.73	7.617%	$191.2677	$191.27	$191.25	$191.30
Purchase #5	$130.63	9.339%	$142.8295	$142.83	$142.85	$142.80
Purchase #6	$148.48	7.660%	$159.8536	$159.85	$159.85	$159.90
Purchase #7	$35.45	5.296%	$37.3274	$37.33	$37.35	$37.30
7 purchase totals =	$950.00		$1,026.9610	$1,026.96	$1,027.00	$1,027.00