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	$223.53	12.112%	$250.604	$250.60	$250.60	$250.60
Purchase #2	$60.78	4.524%	$63.5297	$63.53	$63.55	$63.50
Purchase #3	$187.71	11.849%	$209.9518	$209.95	$209.95	$210.00
Purchase #4	$50.63	6.590%	$53.9665	$53.97	$53.95	$54.00
Purchase #5	$172.79	7.357%	$185.5022	$185.50	$185.50	$185.50
Purchase #6	$85.79	12.233%	$96.2847	$96.28	$96.30	$96.30
Purchase #7	$82.45	3.699%	$85.4998	$85.50	$85.50	$85.50
7 purchase totals =	$863.68		$945.3387	$945.33	$945.35	$945.40