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	$166.74	8.826%	$181.4565	$181.46	$181.45	$181.50
Purchase #2	$194.69	8.216%	$210.6857	$210.69	$210.70	$210.70
Purchase #3	$163.54	13.581%	$185.7504	$185.75	$185.75	$185.80
Purchase #4	$87.45	10.689%	$96.7975	$96.80	$96.80	$96.80
Purchase #5	$82.35	10.359%	$90.8806	$90.88	$90.90	$90.90
Purchase #6	$171.97	3.395%	$177.8084	$177.81	$177.80	$177.80
Purchase #7	$173.26	4.157%	$180.4624	$180.46	$180.45	$180.50
7 purchase totals =	$1,040.00		$1,123.8415	$1,123.85	$1,123.85	$1,124.00