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	$175.67	5.203%	$184.8101	$184.81	$184.80	$184.80
Purchase #2	$249.37	12.297%	$280.035	$280.04	$280.05	$280.00
Purchase #3	$41.61	9.669%	$45.6333	$45.63	$45.65	$45.60
Purchase #4	$112.35	5.840%	$118.9112	$118.91	$118.90	$118.90
Purchase #5	$98.34	7.353%	$105.5709	$105.57	$105.55	$105.60
Purchase #6	$194.53	4.296%	$202.887	$202.89	$202.90	$202.90
Purchase #7	$125.42	12.453%	$141.0386	$141.04	$141.05	$141.00
7 purchase totals =	$997.29		$1,078.8861	$1,078.89	$1,078.90	$1,078.80