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	$187.45	10.863%	$207.8127	$207.81	$207.80	$207.80
Purchase #2	$60.86	10.280%	$67.1164	$67.12	$67.10	$67.10
Purchase #3	$184.33	3.539%	$190.8534	$190.85	$190.85	$190.90
Purchase #4	$228.73	3.661%	$237.1038	$237.10	$237.10	$237.10
Purchase #5	$203.98	10.279%	$224.9471	$224.95	$224.95	$224.90
Purchase #6	$30.72	6.495%	$32.7153	$32.72	$32.70	$32.70
Purchase #7	$152.97	9.661%	$167.7484	$167.75	$167.75	$167.70
7 purchase totals =	$1,049.04		$1,128.2971	$1,128.30	$1,128.25	$1,128.20