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	$145.53	11.710%	$162.5716	$162.57	$162.55	$162.60
Purchase #2	$117.68	3.158%	$121.3963	$121.40	$121.40	$121.40
Purchase #3	$74.95	4.684%	$78.4607	$78.46	$78.45	$78.50
Purchase #4	$28.91	9.314%	$31.6027	$31.60	$31.60	$31.60
Purchase #5	$181.57	10.233%	$200.1501	$200.15	$200.15	$200.20
Purchase #6	$110.79	6.231%	$117.6933	$117.69	$117.70	$117.70
Purchase #7	$70.46	12.302%	$79.128	$79.13	$79.15	$79.10
7 purchase totals =	$729.89		$791.0027	$791.00	$791.00	$791.10