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	$82.45	5.152%	$86.6978	$86.70	$86.70	$86.70
Purchase #2	$155.72	7.646%	$167.6264	$167.63	$167.65	$167.60
Purchase #3	$242.54	13.427%	$275.1058	$275.11	$275.10	$275.10
Purchase #4	$189.35	10.172%	$208.6107	$208.61	$208.60	$208.60
Purchase #5	$99.88	11.703%	$111.569	$111.57	$111.55	$111.60
Purchase #6	$72.90	12.790%	$82.2239	$82.22	$82.20	$82.20
Purchase #7	$214.29	4.789%	$224.5523	$224.55	$224.55	$224.60
7 purchase totals =	$1,057.13		$1,156.3859	$1,156.39	$1,156.35	$1,156.40