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	$161.62	9.297%	$176.6458	$176.65	$176.65	$176.60
Purchase #2	$62.28	8.448%	$67.5414	$67.54	$67.55	$67.50
Purchase #3	$57.89	12.498%	$65.1251	$65.13	$65.15	$65.10
Purchase #4	$59.51	8.223%	$64.4035	$64.40	$64.40	$64.40
Purchase #5	$48.29	8.584%	$52.4352	$52.44	$52.45	$52.40
Purchase #6	$53.93	13.601%	$61.265	$61.27	$61.25	$61.30
Purchase #7	$196.65	4.524%	$205.5464	$205.55	$205.55	$205.50
7 purchase totals =	$640.17		$692.9624	$692.98	$693.00	$692.80