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	$162.42	8.622%	$176.4239	$176.42	$176.40	$176.40
Purchase #2	$41.56	5.587%	$43.882	$43.88	$43.90	$43.90
Purchase #3	$41.32	10.279%	$45.5673	$45.57	$45.55	$45.60
Purchase #4	$211.76	13.413%	$240.1634	$240.16	$240.15	$240.20
Purchase #5	$94.72	4.359%	$98.8488	$98.85	$98.85	$98.80
Purchase #6	$179.35	6.524%	$191.0508	$191.05	$191.05	$191.10
Purchase #7	$118.76	12.532%	$133.643	$133.64	$133.65	$133.60
7 purchase totals =	$849.89		$929.5792	$929.57	$929.55	$929.60