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	$153.91	6.833%	$164.4267	$164.43	$164.45	$164.40
Purchase #2	$186.83	4.784%	$195.7679	$195.77	$195.75	$195.80
Purchase #3	$181.35	9.269%	$198.1593	$198.16	$198.15	$198.20
Purchase #4	$182.76	7.596%	$196.6424	$196.64	$196.65	$196.60
Purchase #5	$215.93	12.733%	$243.4244	$243.42	$243.40	$243.40
Purchase #6	$104.39	5.291%	$109.9133	$109.91	$109.90	$109.90
Purchase #7	$110.34	3.558%	$114.2659	$114.27	$114.25	$114.30
7 purchase totals =	$1,135.51		$1,222.5999	$1,222.60	$1,222.55	$1,222.60