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	$56.26	10.454%	$62.1414	$62.14	$62.15	$62.10
Purchase #2	$80.97	12.218%	$90.8629	$90.86	$90.85	$90.90
Purchase #3	$33.57	6.571%	$35.7759	$35.78	$35.80	$35.80
Purchase #4	$202.73	13.713%	$230.5304	$230.53	$230.55	$230.50
Purchase #5	$128.65	11.837%	$143.8783	$143.88	$143.90	$143.90
Purchase #6	$102.96	13.403%	$116.7597	$116.76	$116.75	$116.80
Purchase #7	$180.98	13.503%	$205.4177	$205.42	$205.40	$205.40
7 purchase totals =	$786.12		$885.3663	$885.37	$885.40	$885.40