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	$43.63	9.615%	$47.825	$47.83	$47.85	$47.80
Purchase #2	$93.86	3.195%	$96.8588	$96.86	$96.85	$96.90
Purchase #3	$144.53	3.406%	$149.4527	$149.45	$149.45	$149.50
Purchase #4	$151.42	11.210%	$168.3942	$168.39	$168.40	$168.40
Purchase #5	$57.35	10.704%	$63.4887	$63.49	$63.50	$63.50
Purchase #6	$181.98	4.276%	$189.7615	$189.76	$189.75	$189.80
Purchase #7	$249.82	12.530%	$281.1224	$281.12	$281.10	$281.10
7 purchase totals =	$922.59		$996.9033	$996.90	$996.90	$997.00