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	$212.68	5.739%	$224.8857	$224.89	$224.90	$224.90
Purchase #2	$155.64	13.189%	$176.1674	$176.17	$176.15	$176.20
Purchase #3	$85.88	4.140%	$89.4354	$89.44	$89.45	$89.40
Purchase #4	$60.55	7.571%	$65.1342	$65.13	$65.15	$65.10
Purchase #5	$71.73	6.406%	$76.325	$76.33	$76.35	$76.30
Purchase #6	$55.79	5.607%	$58.9181	$58.92	$58.90	$58.90
Purchase #7	$63.67	5.682%	$67.2877	$67.29	$67.30	$67.30
7 purchase totals =	$705.94		$758.1535	$758.17	$758.20	$758.10