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	$58.40	5.312%	$61.5022	$61.50	$61.50	$61.50
Purchase #2	$157.43	12.352%	$176.8758	$176.88	$176.90	$176.90
Purchase #3	$171.38	12.859%	$193.4178	$193.42	$193.40	$193.40
Purchase #4	$75.56	8.197%	$81.7537	$81.75	$81.75	$81.80
Purchase #5	$94.79	4.597%	$99.1475	$99.15	$99.15	$99.10
Purchase #6	$38.49	13.238%	$43.5853	$43.59	$43.60	$43.60
Purchase #7	$92.59	6.464%	$98.575	$98.58	$98.60	$98.60
7 purchase totals =	$688.64		$754.8573	$754.87	$754.90	$754.90