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	$154.42	11.265%	$171.8154	$171.82	$171.80	$171.80
Purchase #2	$95.88	4.765%	$100.4487	$100.45	$100.45	$100.40
Purchase #3	$66.25	7.410%	$71.1591	$71.16	$71.15	$71.20
Purchase #4	$85.91	7.666%	$92.4959	$92.50	$92.50	$92.50
Purchase #5	$171.34	13.844%	$195.0603	$195.06	$195.05	$195.10
Purchase #6	$236.79	5.387%	$249.5459	$249.55	$249.55	$249.50
Purchase #7	$219.59	8.632%	$238.545	$238.55	$238.55	$238.50
7 purchase totals =	$1,030.18		$1,119.0703	$1,119.09	$1,119.05	$1,119.00