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	$224.86	8.254%	$243.4199	$243.42	$243.40	$243.40
Purchase #2	$112.64	5.870%	$119.252	$119.25	$119.25	$119.30
Purchase #3	$140.72	13.626%	$159.8945	$159.89	$159.90	$159.90
Purchase #4	$38.89	4.330%	$40.5739	$40.57	$40.55	$40.60
Purchase #5	$63.77	4.144%	$66.4126	$66.41	$66.40	$66.40
Purchase #6	$101.61	8.675%	$110.4247	$110.42	$110.40	$110.40
Purchase #7	$174.48	6.871%	$186.4685	$186.47	$186.45	$186.50
7 purchase totals =	$856.97		$926.4461	$926.43	$926.35	$926.50