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	$209.29	7.424%	$224.8277	$224.83	$224.85	$224.80
Purchase #2	$79.57	13.401%	$90.2332	$90.23	$90.25	$90.20
Purchase #3	$173.55	10.365%	$191.5385	$191.54	$191.55	$191.50
Purchase #4	$39.86	11.868%	$44.5906	$44.59	$44.60	$44.60
Purchase #5	$200.74	11.218%	$223.259	$223.26	$223.25	$223.30
Purchase #6	$59.59	9.195%	$65.0693	$65.07	$65.05	$65.10
Purchase #7	$55.89	11.166%	$62.1307	$62.13	$62.15	$62.10
7 purchase totals =	$818.49		$901.6490	$901.65	$901.70	$901.60