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	$36.39	4.838%	$38.1505	$38.15	$38.15	$38.20
Purchase #2	$154.35	10.688%	$170.8469	$170.85	$170.85	$170.80
Purchase #3	$26.88	9.360%	$29.396	$29.40	$29.40	$29.40
Purchase #4	$63.69	11.330%	$70.9061	$70.91	$70.90	$70.90
Purchase #5	$91.38	4.211%	$95.228	$95.23	$95.25	$95.20
Purchase #6	$52.83	3.446%	$54.6505	$54.65	$54.65	$54.70
Purchase #7	$191.86	7.689%	$206.6121	$206.61	$206.60	$206.60
7 purchase totals =	$617.38		$665.7901	$665.80	$665.80	$665.80