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	$56.47	10.319%	$62.2971	$62.30	$62.30	$62.30
Purchase #2	$50.91	5.622%	$53.7722	$53.77	$53.75	$53.80
Purchase #3	$168.86	3.265%	$174.3733	$174.37	$174.35	$174.40
Purchase #4	$75.62	9.563%	$82.8515	$82.85	$82.85	$82.90
Purchase #5	$98.29	10.446%	$108.5574	$108.56	$108.55	$108.60
Purchase #6	$151.61	7.378%	$162.7958	$162.80	$162.80	$162.80
Purchase #7	$50.62	6.516%	$53.9184	$53.92	$53.90	$53.90
7 purchase totals =	$652.38		$698.5657	$698.57	$698.50	$698.70