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	$112.50	10.521%	$124.3361	$124.34	$124.35	$124.30
Purchase #2	$11.56	10.315%	$12.7524	$12.75	$12.75	$12.80
Purchase #3	$121.36	7.855%	$130.8928	$130.89	$130.90	$130.90
Purchase #4	$122.89	9.147%	$134.1307	$134.13	$134.15	$134.10
Purchase #5	$124.64	10.631%	$137.8905	$137.89	$137.90	$137.90
Purchase #6	$65.54	9.669%	$71.8771	$71.88	$71.90	$71.90
Purchase #7	$118.71	4.214%	$123.7124	$123.71	$123.70	$123.70
7 purchase totals =	$677.20		$735.5920	$735.59	$735.65	$735.60