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	$66.27	12.863%	$74.7943	$74.79	$74.80	$74.80
Purchase #2	$186.71	4.177%	$194.5089	$194.51	$194.50	$194.50
Purchase #3	$132.45	13.826%	$150.7625	$150.76	$150.75	$150.80
Purchase #4	$88.71	7.410%	$95.2834	$95.28	$95.30	$95.30
Purchase #5	$223.96	9.408%	$245.0302	$245.03	$245.05	$245.00
Purchase #6	$132.32	7.644%	$142.4345	$142.43	$142.45	$142.40
Purchase #7	$108.81	4.696%	$113.9197	$113.92	$113.90	$113.90
7 purchase totals =	$939.23		$1,016.7335	$1,016.72	$1,016.75	$1,016.70