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	$231.32	8.445%	$250.855	$250.86	$250.85	$250.90
Purchase #2	$13.93	12.223%	$15.6327	$15.63	$15.65	$15.60
Purchase #3	$194.30	6.273%	$206.4884	$206.49	$206.50	$206.50
Purchase #4	$113.39	13.604%	$128.8156	$128.82	$128.80	$128.80
Purchase #5	$54.29	10.417%	$59.9454	$59.95	$59.95	$59.90
Purchase #6	$81.26	10.411%	$89.72	$89.72	$89.70	$89.70
Purchase #7	$199.42	9.376%	$218.1176	$218.12	$218.10	$218.10
7 purchase totals =	$887.91		$969.5747	$969.59	$969.55	$969.50