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	$205.40	6.116%	$217.9623	$217.96	$217.95	$218.00
Purchase #2	$164.90	6.405%	$175.4618	$175.46	$175.45	$175.50
Purchase #3	$84.42	7.589%	$90.8266	$90.83	$90.85	$90.80
Purchase #4	$234.49	6.494%	$249.7178	$249.72	$249.70	$249.70
Purchase #5	$39.56	8.133%	$42.7774	$42.78	$42.80	$42.80
Purchase #6	$146.53	4.854%	$153.6426	$153.64	$153.65	$153.60
Purchase #7	$158.92	3.206%	$164.015	$164.02	$164.00	$164.00
7 purchase totals =	$1,034.22		$1,094.4035	$1,094.41	$1,094.40	$1,094.40