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	$229.64	9.551%	$251.5729	$251.57	$251.55	$251.60
Purchase #2	$91.73	8.389%	$99.4252	$99.43	$99.45	$99.40
Purchase #3	$36.67	6.576%	$39.0814	$39.08	$39.10	$39.10
Purchase #4	$123.35	9.160%	$134.6489	$134.65	$134.65	$134.60
Purchase #5	$59.31	3.740%	$61.5282	$61.53	$61.55	$61.50
Purchase #6	$90.91	12.860%	$102.601	$102.60	$102.60	$102.60
Purchase #7	$200.25	10.671%	$221.6187	$221.62	$221.60	$221.60
7 purchase totals =	$831.86		$910.4763	$910.48	$910.50	$910.40