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	$63.53	12.158%	$71.254	$71.25	$71.25	$71.30
Purchase #2	$78.80	5.796%	$83.3672	$83.37	$83.35	$83.40
Purchase #3	$57.90	7.873%	$62.4585	$62.46	$62.45	$62.50
Purchase #4	$148.44	13.694%	$168.7674	$168.77	$168.75	$168.80
Purchase #5	$91.80	5.540%	$96.8857	$96.89	$96.90	$96.90
Purchase #6	$155.80	7.258%	$167.108	$167.11	$167.10	$167.10
Purchase #7	$64.77	12.485%	$72.8565	$72.86	$72.85	$72.90
7 purchase totals =	$661.04		$722.6973	$722.71	$722.65	$722.90