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	$233.46	11.202%	$259.6122	$259.61	$259.60	$259.60
Purchase #2	$176.78	11.632%	$197.343	$197.34	$197.35	$197.30
Purchase #3	$59.28	13.617%	$67.3522	$67.35	$67.35	$67.40
Purchase #4	$169.29	9.438%	$185.2676	$185.27	$185.25	$185.30
Purchase #5	$131.32	11.814%	$146.8341	$146.83	$146.85	$146.80
Purchase #6	$94.82	10.701%	$104.9667	$104.97	$104.95	$105.00
Purchase #7	$38.35	3.700%	$39.769	$39.77	$39.75	$39.80
7 purchase totals =	$903.30		$1,001.1448	$1,001.14	$1,001.10	$1,001.20