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	$222.63	13.804%	$253.3618	$253.36	$253.35	$253.40
Purchase #2	$136.96	10.615%	$151.4983	$151.50	$151.50	$151.50
Purchase #3	$243.92	10.712%	$270.0487	$270.05	$270.05	$270.00
Purchase #4	$40.83	4.820%	$42.798	$42.80	$42.80	$42.80
Purchase #5	$103.85	3.872%	$107.8711	$107.87	$107.85	$107.90
Purchase #6	$162.87	10.463%	$179.9111	$179.91	$179.90	$179.90
Purchase #7	$201.40	10.435%	$222.4161	$222.42	$222.40	$222.40
7 purchase totals =	$1,112.46		$1,227.9051	$1,227.91	$1,227.85	$1,227.90