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	$174.69	10.366%	$192.7984	$192.80	$192.80	$192.80
Purchase #2	$38.71	12.653%	$43.608	$43.61	$43.60	$43.60
Purchase #3	$229.91	3.690%	$238.3937	$238.39	$238.40	$238.40
Purchase #4	$72.38	12.703%	$81.5744	$81.57	$81.55	$81.60
Purchase #5	$108.78	10.662%	$120.3781	$120.38	$120.40	$120.40
Purchase #6	$47.91	10.523%	$52.9516	$52.95	$52.95	$53.00
Purchase #7	$82.53	10.843%	$91.4787	$91.48	$91.50	$91.50
7 purchase totals =	$754.91		$821.1829	$821.18	$821.20	$821.30