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	$98.53	11.117%	$109.4836	$109.48	$109.50	$109.50
Purchase #2	$25.31	9.227%	$27.6454	$27.65	$27.65	$27.60
Purchase #3	$121.77	12.223%	$136.6539	$136.65	$136.65	$136.70
Purchase #4	$196.93	4.819%	$206.4201	$206.42	$206.40	$206.40
Purchase #5	$250.88	11.617%	$280.0247	$280.02	$280.00	$280.00
Purchase #6	$180.86	13.687%	$205.6143	$205.61	$205.60	$205.60
Purchase #7	$77.41	10.708%	$85.6991	$85.70	$85.70	$85.70
7 purchase totals =	$951.69		$1,051.5411	$1,051.53	$1,051.50	$1,051.50