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	$166.55	4.557%	$174.1397	$174.14	$174.15	$174.10
Purchase #2	$59.89	8.664%	$65.0789	$65.08	$65.10	$65.10
Purchase #3	$156.89	5.646%	$165.748	$165.75	$165.75	$165.70
Purchase #4	$100.90	10.281%	$111.2735	$111.27	$111.25	$111.30
Purchase #5	$53.53	3.493%	$55.3998	$55.40	$55.40	$55.40
Purchase #6	$106.64	13.871%	$121.432	$121.43	$121.45	$121.40
Purchase #7	$172.68	10.455%	$190.7337	$190.73	$190.75	$190.70
7 purchase totals =	$817.08		$883.8056	$883.80	$883.85	$883.70