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	$106.76	12.269%	$119.8584	$119.86	$119.85	$119.90
Purchase #2	$208.45	13.781%	$237.1765	$237.18	$237.20	$237.20
Purchase #3	$64.42	4.168%	$67.105	$67.11	$67.10	$67.10
Purchase #4	$20.77	5.818%	$21.9784	$21.98	$22.00	$22.00
Purchase #5	$239.59	3.646%	$248.3255	$248.33	$248.35	$248.30
Purchase #6	$82.84	9.327%	$90.5665	$90.57	$90.55	$90.60
Purchase #7	$218.81	11.280%	$243.4918	$243.49	$243.50	$243.50
7 purchase totals =	$941.64		$1,028.5021	$1,028.52	$1,028.55	$1,028.60