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	$201.64	12.661%	$227.1696	$227.17	$227.15	$227.20
Purchase #2	$45.46	3.774%	$47.1757	$47.18	$47.20	$47.20
Purchase #3	$209.25	7.449%	$224.837	$224.84	$224.85	$224.80
Purchase #4	$195.89	10.185%	$215.8414	$215.84	$215.85	$215.80
Purchase #5	$150.27	12.404%	$168.9095	$168.91	$168.90	$168.90
Purchase #6	$58.98	12.265%	$66.2139	$66.21	$66.20	$66.20
Purchase #7	$46.56	10.292%	$51.352	$51.35	$51.35	$51.40
7 purchase totals =	$908.05		$1,001.4991	$1,001.50	$1,001.50	$1,001.50