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	$32.38	12.678%	$36.4851	$36.49	$36.50	$36.50
Purchase #2	$71.30	10.728%	$78.9491	$78.95	$78.95	$78.90
Purchase #3	$78.31	3.388%	$80.9631	$80.96	$80.95	$81.00
Purchase #4	$237.88	12.110%	$266.6873	$266.69	$266.70	$266.70
Purchase #5	$123.57	4.535%	$129.1739	$129.17	$129.15	$129.20
Purchase #6	$173.41	4.295%	$180.858	$180.86	$180.85	$180.90
Purchase #7	$160.70	4.771%	$168.367	$168.37	$168.35	$168.40
7 purchase totals =	$877.55		$941.4835	$941.49	$941.45	$941.60