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	$246.87	7.141%	$264.499	$264.50	$264.50	$264.50
Purchase #2	$35.55	3.432%	$36.7701	$36.77	$36.75	$36.80
Purchase #3	$10.80	9.324%	$11.807	$11.81	$11.80	$11.80
Purchase #4	$56.77	9.270%	$62.0326	$62.03	$62.05	$62.00
Purchase #5	$50.85	4.579%	$53.1784	$53.18	$53.20	$53.20
Purchase #6	$92.75	4.560%	$96.9794	$96.98	$97.00	$97.00
Purchase #7	$130.79	8.633%	$142.0811	$142.08	$142.10	$142.10
7 purchase totals =	$624.38		$667.3476	$667.35	$667.40	$667.40