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	$16.64	4.825%	$17.4429	$17.44	$17.45	$17.40
Purchase #2	$149.33	10.805%	$165.4651	$165.47	$165.45	$165.50
Purchase #3	$76.50	6.396%	$81.3929	$81.39	$81.40	$81.40
Purchase #4	$19.46	10.699%	$21.542	$21.54	$21.55	$21.50
Purchase #5	$139.59	8.117%	$150.9205	$150.92	$150.90	$150.90
Purchase #6	$235.82	10.845%	$261.3947	$261.39	$261.40	$261.40
Purchase #7	$64.31	6.341%	$68.3879	$68.39	$68.40	$68.40
7 purchase totals =	$701.65		$766.5460	$766.54	$766.55	$766.50