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	$161.75	9.583%	$177.2505	$177.25	$177.25	$177.30
Purchase #2	$237.41	3.435%	$245.565	$245.57	$245.55	$245.60
Purchase #3	$28.46	10.612%	$31.4802	$31.48	$31.50	$31.50
Purchase #4	$210.31	8.117%	$227.3809	$227.38	$227.40	$227.40
Purchase #5	$82.31	8.552%	$89.3492	$89.35	$89.35	$89.30
Purchase #6	$48.65	9.857%	$53.4454	$53.45	$53.45	$53.40
Purchase #7	$169.50	6.432%	$180.4022	$180.40	$180.40	$180.40
7 purchase totals =	$938.39		$1,004.8734	$1,004.88	$1,004.90	$1,004.90