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	$197.90	9.429%	$216.56	$216.56	$216.55	$216.60
Purchase #2	$51.65	6.265%	$54.8859	$54.89	$54.90	$54.90
Purchase #3	$179.81	3.583%	$186.2526	$186.25	$186.25	$186.30
Purchase #4	$116.50	3.609%	$120.7045	$120.70	$120.70	$120.70
Purchase #5	$222.31	9.502%	$243.4339	$243.43	$243.45	$243.40
Purchase #6	$109.77	12.524%	$123.5176	$123.52	$123.50	$123.50
Purchase #7	$8.39	8.805%	$9.1287	$9.13	$9.15	$9.10
7 purchase totals =	$886.33		$954.4832	$954.48	$954.50	$954.50