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	$103.60	10.548%	$114.5277	$114.53	$114.55	$114.50
Purchase #2	$110.92	12.341%	$124.6086	$124.61	$124.60	$124.60
Purchase #3	$106.82	4.494%	$111.6205	$111.62	$111.60	$111.60
Purchase #4	$186.37	3.432%	$192.7662	$192.77	$192.75	$192.80
Purchase #5	$178.74	9.739%	$196.1475	$196.15	$196.15	$196.10
Purchase #6	$224.27	5.871%	$237.4369	$237.44	$237.45	$237.40
Purchase #7	$69.57	11.698%	$77.7083	$77.71	$77.70	$77.70
7 purchase totals =	$980.29		$1,054.8157	$1,054.83	$1,054.80	$1,054.70