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	$248.52	13.360%	$281.7223	$281.72	$281.70	$281.70
Purchase #2	$237.71	9.684%	$260.7298	$260.73	$260.75	$260.70
Purchase #3	$53.42	11.458%	$59.5409	$59.54	$59.55	$59.50
Purchase #4	$55.28	7.758%	$59.5686	$59.57	$59.55	$59.60
Purchase #5	$172.99	8.123%	$187.042	$187.04	$187.05	$187.00
Purchase #6	$218.78	8.616%	$237.6301	$237.63	$237.65	$237.60
Purchase #7	$104.81	4.116%	$109.124	$109.12	$109.10	$109.10
7 purchase totals =	$1,091.51		$1,195.3577	$1,195.35	$1,195.35	$1,195.20