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	$130.37	10.424%	$143.9598	$143.96	$143.95	$144.00
Purchase #2	$56.55	4.589%	$59.1451	$59.15	$59.15	$59.10
Purchase #3	$152.59	11.290%	$169.8174	$169.82	$169.80	$169.80
Purchase #4	$43.45	10.779%	$48.1335	$48.13	$48.15	$48.10
Purchase #5	$80.86	6.583%	$86.183	$86.18	$86.20	$86.20
Purchase #6	$100.40	9.638%	$110.0766	$110.08	$110.10	$110.10
Purchase #7	$209.34	9.187%	$228.5721	$228.57	$228.55	$228.60
7 purchase totals =	$773.56		$845.8875	$845.89	$845.90	$845.90