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	$57.75	4.280%	$60.2217	$60.22	$60.20	$60.20
Purchase #2	$52.69	3.576%	$54.5742	$54.57	$54.55	$54.60
Purchase #3	$39.75	7.113%	$42.5774	$42.58	$42.60	$42.60
Purchase #4	$86.39	7.445%	$92.8217	$92.82	$92.80	$92.80
Purchase #5	$165.44	12.256%	$185.7163	$185.72	$185.70	$185.70
Purchase #6	$78.93	9.147%	$86.1497	$86.15	$86.15	$86.10
Purchase #7	$76.91	9.694%	$84.3657	$84.37	$84.35	$84.40
7 purchase totals =	$557.86		$606.4267	$606.43	$606.35	$606.40