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	$36.37	4.486%	$38.0016	$38.00	$38.00	$38.00
Purchase #2	$242.78	10.648%	$268.6312	$268.63	$268.65	$268.60
Purchase #3	$206.38	10.768%	$228.603	$228.60	$228.60	$228.60
Purchase #4	$208.91	4.577%	$218.4718	$218.47	$218.45	$218.50
Purchase #5	$102.88	12.149%	$115.3789	$115.38	$115.40	$115.40
Purchase #6	$215.29	12.469%	$242.1345	$242.13	$242.15	$242.10
Purchase #7	$37.56	10.780%	$41.609	$41.61	$41.60	$41.60
7 purchase totals =	$1,050.17		$1,152.8300	$1,152.82	$1,152.85	$1,152.80