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	$29.88	7.447%	$32.1052	$32.11	$32.10	$32.10
Purchase #2	$16.82	6.141%	$17.8529	$17.85	$17.85	$17.90
Purchase #3	$76.74	7.673%	$82.6283	$82.63	$82.65	$82.60
Purchase #4	$142.41	9.218%	$155.5374	$155.54	$155.55	$155.50
Purchase #5	$203.32	9.623%	$222.8855	$222.89	$222.90	$222.90
Purchase #6	$83.84	10.758%	$92.8595	$92.86	$92.85	$92.90
Purchase #7	$119.60	6.849%	$127.7914	$127.79	$127.80	$127.80
7 purchase totals =	$672.61		$731.6602	$731.67	$731.70	$731.70