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	$198.42	3.729%	$205.8191	$205.82	$205.80	$205.80
Purchase #2	$59.25	13.430%	$67.2073	$67.21	$67.20	$67.20
Purchase #3	$75.33	13.434%	$85.4498	$85.45	$85.45	$85.40
Purchase #4	$117.63	10.622%	$130.1247	$130.12	$130.10	$130.10
Purchase #5	$93.59	12.209%	$105.0164	$105.02	$105.00	$105.00
Purchase #6	$160.60	8.715%	$174.5963	$174.60	$174.60	$174.60
Purchase #7	$250.96	11.872%	$280.754	$280.75	$280.75	$280.80
7 purchase totals =	$955.78		$1,048.9676	$1,048.97	$1,048.90	$1,048.90