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	$139.61	10.334%	$154.0373	$154.04	$154.05	$154.00
Purchase #2	$96.84	8.208%	$104.7886	$104.79	$104.80	$104.80
Purchase #3	$105.43	10.339%	$116.3304	$116.33	$116.35	$116.30
Purchase #4	$207.25	9.667%	$227.2849	$227.28	$227.30	$227.30
Purchase #5	$99.72	8.801%	$108.4964	$108.50	$108.50	$108.50
Purchase #6	$167.61	7.744%	$180.5897	$180.59	$180.60	$180.60
Purchase #7	$132.25	10.790%	$146.5198	$146.52	$146.50	$146.50
7 purchase totals =	$948.71		$1,038.0471	$1,038.05	$1,038.10	$1,038.00