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	$140.51	4.184%	$146.3889	$146.39	$146.40	$146.40
Purchase #2	$237.92	12.794%	$268.3595	$268.36	$268.35	$268.40
Purchase #3	$113.38	5.150%	$119.2191	$119.22	$119.20	$119.20
Purchase #4	$209.57	9.697%	$229.892	$229.89	$229.90	$229.90
Purchase #5	$53.45	4.334%	$55.7665	$55.77	$55.75	$55.80
Purchase #6	$183.50	6.185%	$194.8495	$194.85	$194.85	$194.80
Purchase #7	$101.60	4.253%	$105.921	$105.92	$105.90	$105.90
7 purchase totals =	$1,039.93		$1,120.3965	$1,120.40	$1,120.35	$1,120.40